[21] APPL No; 616,4”
`ml Ffl°"‘ M“ 19'1"‘
`mmanwuuonv-m
`“Highly Stqoeontlollad and Eflicient Preparation of the
`[53] Collfilllliltitll-1'11-Plfl of 3H: Nth 509.033. Fat 29. 19941
`“°‘f’°,§°“~ E“°“"i°"i°”"“‘““5’ D°°°“”‘°1 C“-*°‘°"°) 5”‘
`[51]
`Int. CL‘ _..............;.................... cum 305114
`
`[52] us. Cl. ...........................,_
`............ 5491510 g3?;1= °‘ "1’ 1 0‘? °"'“m~ "°5'~ 59* ”°- '5' PP“
`[53] Fidd ul.'Seamcl1 ..................................... 549l51D
`’
`“Novel Biologically Active 'I3ixo1 Ana]1ogI1es:Bacca1:in ]]I
`13—(N—(p—C1h1:robenz°1'1)—(2‘R,3'S)n3'-ph=nyfisosa=ina9=)
`d_
`Bagcgfin
`_B¢nz
`;C‘S)_3.{P_cmm?phmymso]:Iuimm);.13Gemgm at :£’"§§3:f,_‘
`
`[50]
`
`-
`
`References Cited
`U-.S.PA'1‘EN'I‘ DOCUMENTS
`
`"
`
`-
`
`of me Vicinal Oxyaminatlon Reacfion who
`Asymmctic Indneeion to the Hazrnisynflacsis of ma and
`Analogues”, 1.. Mnngatal ee :11, Tea-uhedm-1, val. 45, No. 13,
`pp. 4177 to 4190, 1939.
`
`US005688977A
`'
`' 5,688,977
`[11] Patent Number:
`Umted States Patent
`Sisti et aL
`[45] Date of Patent:
`Nov. 18, 1997
`
`
`[193
`
`[54]
`
`[751
`
`n-11111101) 11011 DOCETAXEL SYNTHESIS
`'
`.
`Invenroesz Nicholas J. sins, Jcficrsonvillc;
`33”” 3‘ 5‘‘'‘“‘'°“' M°“°“~ "°"'_ "f
`-
`
`“Synthesis of Bialogimlly Active Taxol Analogues with
`ModificdPl1cn)rlisoserine Side Ch.ai.ns",Goc1-gctal..J.Med.
`c;.,,,,,,- 1992, 35, 42304337,
`'
`-
`"BiologicallyActivcmaAnalogues with Dc.lctodA—Ri11g
`Side Chain Substituents and Variable C-2' Configmafions”,
`
`Mawr, Pa.
`
`_
`
`“New and Efficient Approaches to the Selnisynthcsis of
`'l'axo1anditsC—l3SideCt1ainAna1ogsbyMe-ansof
`B—Lactam Synthon Mlclhod", Ojima ct 31,
`vol.
`48, No. 34, pp. 6985-7012, 1992.
`“1nn:eavedProcect1oonndEste1iheetionofePrec1nsonoru1e
`
`......................... 5491510
`011993 Denis etal.
`Re 34,211
`311939 Cnlinetal. .........
`......... 549/510
`4,314,470
`a/19:9 Colinetal. ,,...................... 5491510
`4,357,553
`.
`.
`511990 Denis em. .................... 5491510
`4,924,011
`_
`P""""'3’ E"“"""”—-‘Ems H; Rm“
`511990 Uulin ml. -..................... 5491510
`4,924,012
`4,960,790 100990 Siallaetal ..................... 5492510 MOM): Assn: or Fmn—T1mothy J. Martin: Mxchacl R.
`5,015,744
`5/1991 I-1019011 ...........
`................._. 5491510
`B99509
`5,136,060
`0/1992 Hohon .................
`........ 549510
`5,399,726
`311995 I-Iolmn etal. _............... 5491510
`5,413,364
`511995 Nioolaouetal.
`....................-. 549510
`5,455,334 110995 I-Iollionet 11L _.................. 549510
`-------mflnu-H"-.
`01995 Gmawmdam at .1 ........... 549510
`5,530,000
` N PATENT
`0,0097!
`5,1990 Eumllmptofi‘
`o5g372gA]_
`snggz Emapgu P‘ on ‘
`268‘73[1£
`2!1992 France.
`WODUI
`9:199] WIPO.
`OTHER PUBLICATIONS
`
`sonic & Medium! Chm Izrtm. "01- 2. N9 4, pp-
`295-298. 1992.
`
`'
`
`‘
`
`[571
`
`A33TRACT
`
`.
`.
`.
`*5 ‘“°"'°‘1 °f P'°d”.""'3 d°°°“"°1 °°'“1’“"°‘ 3*“ °“°"““'
`hall (f
`dl-CB2
`III and ‘Ill
`$30991115% 91:19‘grin Whergnn
`a
`1s paraded
`genatable
`ny -
`protecting
`group Th; C)’, C10 (31-bgbgnzyloxy groups 311:; mgn
`a11dtl1ecarbol3enzy1oxygrnupatd:e
`C3' mlmgen slte J5 replaced with t-butoxycarbolryl. finally,
`glrjccsnlfilllgconnpolmdis dc{n'(:tec:datC2'byreplncing
`nzy-typeprotectinggroupwi hydrogontoproducc
`docetaxcl. The esteznficauon preferably employs an excess,
`such as six eqtfivalents, of the side chain for each equivalt
`of the C7, C10 #4132 1041”-Uetyl bwmiin 111- Buny-
`loxznneihyl is the nrefenredprotwfins 919119 at C2‘-
`
`24 Claims, No Drawings
`
`ARGENTUM EX1029
`ARGENTUM EX1029
`_
`Page 1
`
`Page 1
`
`

`
`5,688,977
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`
`
`2
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`(t-BOC) group at the C3‘ nitrogen position of the isoserine
`
`
`
`
`
`
`
`
`side chain and a free hydroxy group at the C10 position.
`
`
`
`
`
`
`
`
`
`Several possible syntheses of docetaxel and related com-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`pounds have been reported in the Journal of Organic Chem-
`istry: 1986, 51, 46; 1990, 55, 1957; 1991, 56, 1681; 1991,
`
`
`
`
`
`
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`
`
`
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`56, 6939; I992, 57 4320; 1992, 57 6387; and 1993, 58, 255.
`
`
`
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`
`
`
`
`
`In order to successfully synthesize docetaxel, convenient
`
`
`
`
`
`
`access to a chiral, non—racemic side chain and an abundant
`
`
`
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`
`
`natural source of a usable baccatin III backbone as well as
`
`
`
`
`
`
`
`an etfective means of joining the two are necessary.
`
`
`
`
`
`
`
`
`However, the esterification of the side chain to the baccatin
`
`
`
`
`
`
`
`
`III backbone is diflicult because of the hindered C13
`
`
`
`
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`
`
`hydroxyl in the baccatin III backbone which is located
`
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`
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`within the concave region of the hemispherical taxane
`
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`
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`
`
`
`skeleton. This difliculty of synthesis is present both for the
`
`
`
`
`
`
`
`synthesis of docetaxel as well as for the synthesis of pacli-
`taxel.
`
`
`
`
`
`
`
`
`
`One technique for the semi-synthesis of paclitaxel is
`found in co-pending patent application Ser. No. 08/483,081.
`
`
`
`
`
`
`
`In this application, paclitaxel is synthesized from C7 TES
`
`
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`
`
`
`
`
`
`
`
`
`
`
`protected baccatin III with N-carbarnate protected C2‘
`
`
`
`
`hydroxyl-benzyl protected (2R,3S)-3-phenyl
`isoserine
`
`
`
`
`
`
`
`A-ring side chain with a hydrogenable benzyl-type protect-
`
`
`
`
`
`
`ing group, such as a benzyloxymethyl (BOM) protecting
`group at the C2’ location for the side chain. Following the
`
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`
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`
`
`
`condensation of the C7 TES protected baccatin III and the
`
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`the compound may be suitably deprotected,
`side chain,
`
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`acylated, and further deprotected to yield paclitaxel.
`
`
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`
`
`
`
`While, the existing techniques for synthesizing docetaxel
`
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`
`
`
`
`
`
`certainly have merit, there is still a need for improved
`chemical processes which can produce this anti-cancer com-
`
`
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`
`
`
`pound. The present invention is directed to such a procedure
`
`
`
`
`
`
`
`utilizing the N-carbamate protected C2’ hydroxyl benzyl
`protected (2R,3S)-3-phenylisoserine A-ring side chain as
`
`
`
`
`
`
`described in my earlier co-pending application.
`
`
`
`
`
`
`1
`METHOD FOR DOCETAXEL SYNTHESIS
`
`
`
`
`RELATED APPLICATION
`
`
`
`This application is a continuation-in-part of our earlier
`
`
`
`
`
`
`application, Ser. No. 08/609,083, filed Feb. 29, 1996 and
`
`
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`
`
`
`
`
`
`entitled, Intermediate For Docitaxel Synthesis and Produc-
`tion Method T'herefor.
`
`
`
`
`FIELD OF THE INVENTION
`
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`
`
`This invention generally relates to the synthesis of doc-
`
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`
`
`etaxel from precursor compounds. More particularly,
`
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`
`
`
`though. this invention concerns the synthesis of docetaxel
`
`
`
`
`
`
`using a suitably protected 10-deacetyl baccatin III backbone
`
`
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`
`
`which is esterified with a suitably protected side chain acid
`to produce an intermediate that may thereafter be
`
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`
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`
`
`deprotected, acylated and further deprotected to produce
`docetaxel.
`
`
`BACKGROUND OF THE INVENTION
`
`
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`
`20
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`
`25
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`30
`
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`
`35
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`
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`Various taxane compounds are known to exhibit anti-
`
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`
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`tumor activity. As a result of this activity, taxanes have
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`
`received increasing attention in the scientific and medical
`
`
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`
`
`community. Primary among these is a compound known as
`
`
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`
`
`“paclitaxel” which is also referred to in the literature as
`
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`
`
`
`“taxol”. Paclitaxel has been approved for the chemothera-
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`peutic treatment of several ditferent varieties of tumors, and
`
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`the clinical trials indicate that paclitaxel promises a broad
`
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`range of potent anti-leukemic and tumor-inhibiting activity.
`
`
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`
`
`
`Paclitaxel
`is a naturally occurring taxane diterpenoid
`
`
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`
`
`
`
`
`which is found in several species of the yew (genus Taxus,
`
`
`
`
`
`
`
`family Taxaceae). Unfortunately, the concentration of this
`compound is very low. The species of evergreen are also
`
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`
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`
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`
`
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`
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`
`slow growing. Even though the bark of the yew trees
`
`
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`
`
`
`
`typically exhibits the highest concentration of paclitaxel, the
`
`
`
`
`
`
`production of one kilogram of paclitaxel requires approxi-
`
`
`
`
`
`
`
`
`
`mately 16,000 pounds of bark. Thus, the long term prospects
`for the availability of paclitaxel through isolation are dis-
`
`
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`
`
`
`
`
`
`
`couraging.
`While the presence of paclitaxel in the yew tree is in
`
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`
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`
`
`extremely low concentrations, there are a variety of other
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`taxane compounds, such as baccatin III, cephalomannine,
`
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`
`
`10-deacetylbaccatin III, etc., which are also able to be
`
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`extracted from the yew bark. Some of these other taxane
`
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`compounds are more readily extracted in higher yields.
`a relatively high concentration of
`Indeed,
`
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`
`10-deacetylbaccatin III can be extracted from the leaves of
`
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`
`
`the yew as a renewable resource.
`
`
`
`
`Among the various taxane compounds which have been
`
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`
`
`found to exhibit anti-tumor activity is the compound known
`as “docetaxel”. This compound is also sold under the
`
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`
`
`trademark TAXUI'ERE® by Rhone-Poulenc Sante. Doc-
`etaxel has the formula as follows:
`
`
`
`
`
`
`SUMMARY OF THE INVENTION
`
`
`
`
`
`It is an object of the present invention to provide a new,
`
`
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`
`
`useful and elficient protocol for the attachment of a protected
`
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`
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`A-ring side chain to a protected baccatin III skeleton which
`
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`
`
`may then be converted into docetaxel.
`
`
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`
`
`It is still a further object of the present invention to
`
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`
`
`
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`
`
`provide a new and useful protocol for the serni-synthesis of
`
`
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`
`docetaxel in an effort to produce a high yield of docetaxel in
`
`
`
`
`
`
`a cost efficient manner.
`
`
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`
`
`45
`
`Yet another object of the present invention is to provide a
`
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`
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`
`
`
`
`
`method for the production of docetaxel which potentially
`can be scaled to commercial implementation.
`
`
`
`
`According to the present invention, then, a new and useful
`
`
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`
`
`
`
`
`
`
`
`method for producing docetaxel is provided. According to
`
`
`
`
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`
`
`the general method, C7, C10 di-CBZ 10-deacetyl baccatin
`III of the formula:
`
`
`
`
`
`
`t-Bu0
`
`
`
`As may be seen in this formulation, docetaxel is sirnilar-to
`
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`
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`
`paclitaxel except for the inclusion of the t-butoxycarbonyl
`
`65
`
`
`
`PhCH;0C0g
`
`0C02CH2Ph
`
`Formula I
`
`
`
`
`is esterified with an N—CBZ C2‘-protected
`
`
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`
`
`3-phenylisoserine side chain of the formula:
`
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`Page 2
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`Page 2
`
`

`
`5,688,977
`
`
`
`3
`
`0
`Ph/\OJL rm
`pu/:\/ Com
`31>,
`
`Formula 2
`
`4
`
`to form a first intermediate compound of the formula:
`
`
`
`
`
`
`0
`
`PhCHzOCO2
`
`
`
`
`
`
`
`OCO2CHgPl1
`
`
`O
`
`
`
`Pb/\ OJLNH O
`
`/E\J'L
`
`:
`0
`Ph
`
`
`
`op‘
`
`
`I I H
`
`
`:
`
`5
`H0
`
`PIICO2
`
`
`0
`
`
`
`E
`
`;
`
`OAC
`
`
`
`
`
`the carbobenzyloxy group at the C3’ nitrogen site is subse-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`quently replaced with t-BOC to produce the "second inter-
`
`
`
`
`
`
`
`
`mediate compound. The first portion of this reaction is
`
`
`
`
`
`
`
`' accomplished by dissolving the first intermediate compound
`
`
`
`
`
`
`in isopropanol/ethyl acetate in the presence of Pear]rnan’s
`
`catalyst to form a first mixture and then hydrogenating the
`
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`
`
`
`
`
`
`first mixture for at least forty-eight hours. The next step in
`
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`
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`
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`
`
`
`
`
`
`the replacement is accomplished by taking the amine up in
`
`
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`
`
`
`
`
`tetrahydrofuran and then adding a tertiary amine base. The
`addition of the tertiary amine base is followed by the
`
`
`
`
`
`
`
`
`
`addition of di-tert-butyl dicarbonate in order to form C2‘-
`
`
`
`
`
`
`OP1 docetaxel. This second mixture is stirred for about
`
`
`
`
`
`
`
`
`twenty-four hours and reduced in vacuum It is next redis-
`
`
`
`
`
`
`
`
`solved in ethyl acetate, and washed with water and brine.
`
`
`
`
`
`
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`
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`
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`
`
`
`
`This produces an organic phase which may be separated and
`
`
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`
`
`chromotagraphed with ethyl acetatezhexane and/or recrys-
`
`
`
`
`
`
`
`tallized to give the second intermediate compound in puri-
`fied form.
`
`
`The step of deprotecting the second intermediate com-
`
`
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`
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`
`
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`
`
`
`
`
`
`pound is then accomplished by dissolving the second inter-
`
`
`
`
`
`
`
`mediate compound in isopropanol and ethyl acetate in the
`presence of Pearlrnan’s catalyst to form a second mixture.
`
`
`
`
`
`
`The second mixture is then hydrogenated for at least twenty-
`
`
`
`
`
`
`
`four hours.
`
`
`These and other objects of the present invention will
`
`
`
`
`
`
`
`
`
`become more readily appreciated and understood from a
`
`
`
`
`
`
`
`consideration of the following detailed description of the
`
`
`
`
`
`
`
`
`
`
`exemplary embodiments.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`
`
`50
`
`DETAILED DESCRIPTION OF THE
`
`
`EXE.MPLARY Ell/IBODIMENTS
`
`
`
`
`
`
`
`
`
`
`
`The present disclosure is broadly directed to a chemical
`process for the eflicient production of docetaxel as well as
`
`
`
`
`
`
`
`intermediates and precursors therefor. More specifically, the
`
`
`
`
`
`
`
`present invention discloses a new chemical compound in the
`
`
`
`
`
`
`
`form of C7, C10-di-CBZ 10-deacetylbaccatin III as a useful
`
`
`
`
`
`
`intermediate in the production of docetaxel. The C7, C10-
`
`
`
`
`
`
`di-CBZ 10-deacetylbaccatin ]]I is esterified with a
`
`
`
`
`
`
`
`
`
`
`
`3-phenylisoserine acid having a hydrogenable benzyl-type
`protecting group at C2’ to the C13 hydroxyl of the baccatin
`
`
`
`
`
`
`
`
`III backbone. The general process described herein involves
`
`
`
`
`
`
`
`
`the production of the C7, C10-di-CBZ 10-deacetylbaccatin
`
`
`
`
`
`El backbone,
`the production of the suitably protected
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`3-phenylisoserine acid having the hydrogenatable benzyl
`protecting group C2‘,
`the condensation of the two
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`compounds, and the subsequent deprotection, acylation at
`the C3‘ nitrogen site to add the t-butoxycarbonyl group,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`followed by further deprotection to yield docetaxel.
`
`A. Production of C7, C10 dicarbobenzyloxy 10-
`
`
`
`
`
`deacetylbaccatin I[I
`
`
`
`55
`
`
`
`C7, C10 di-CBZ 10-deacetylbaccatin III (Fonnula 1) is
`
`
`
`
`
`
`
`
`
`
`produced by the following reaction:
`Reaction I
`
`
`PhCH1OCOC1
`
`
`
`
`
`HO
`
`
`
`OH
`
`
`
`
`
`
`
`
`
`
`
`
`
`65
`
`
`
`E)Ac
`
`
`
`Page 3
`
`
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`
`
`wherein P1 is a hydrogenable benzyl-type protecting group.
`Next, the C7 , C10 carbobenzyloxy in the first intermediate
`
`
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`
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`
`
`
`compound is replaced with hydrogen and the carbobenzy-
`
`
`
`
`
`
`
`
`
`loxy at the C3‘ nitrogen site is replaced with t-BOC to form
`a second intermediate compound of the formula:
`
`
`
`
`
`
`HO
`0
`
`
`
`
`
`o
`o
`t-BuO/u\1_‘IH
`-
`Pb/\/J\O.‘
`:
`op.
`
`\
`
`:
`I-[0
`:
`PhCO
`
`2
`
`" H
`O
`
`:
`:
`:
`me
`
`
`
`
`
`
`wherein P1 is a hydrogenatable benzyl-type protecting
`group. Thereafter, the second intermediate compound is
`
`
`
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`
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`
`
`
`
`deprotected by replacing P1 with hydrogen thereby to pro-
`duce docetaxel. It is preferred that the hydrogenatable ben-
`
`
`
`
`
`
`
`zyl protecting group be selected from a group consisting of
`
`
`
`
`
`
`
`
`
`
`
`
`
`benzyloxymethyl and benzyl with benzyloxymethyl being
`
`
`
`
`the preferred protecting group.
`During esterification,
`it is preferred that an excess
`
`
`
`
`
`
`
`
`
`
`
`
`
`N—£BZ C2’-protected 3-phenylisoserine be employed, and
`it is desirable that six equivalents of this side chain be used
`
`
`
`
`
`
`
`
`
`for each equivalent of a C7, C10 di-CBZ 10-deacetyl
`
`
`
`
`
`
`
`
`baccatin 111 during esterification. This reaction is preferably
`
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`
`
`performed by dissolving the two compounds in toluene to
`form a first solution after which dimethylarnine pyridine
`
`
`
`
`
`
`
`(DMAP) and a dialkylcarbodiimide is added to the first
`
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`
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`
`
`solution. The dialkylcarbodiimide is preferably in equal
`
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`
`
`
`
`
`
`
`
`
`
`
`proportion to the amount of the side chain compound. This
`dialkylcarboiirnide is selected from a group consisting of a
`
`
`
`
`
`V diisopropylcarbondiimide and dicyelohexylcarbondiimide.
`
`
`
`
`This esterification step is conducted at a first temperature of
`
`
`
`
`
`
`about 60° to 80° C. for a first interval of time, approximately
`
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`
`
`
`
`
`
`one to five hours after which the solution is allowed to cool
`
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`
`
`
`
`
`
`to room temperature. Next, an equal volume of diethyl ether
`
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`
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`
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`
`
`is added, and the resulting solution is cooled to a reduced
`
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`
`
`
`
`second temperature of 0° C. or less for a second interval of
`
`
`
`
`
`
`about twenty-four hours.
`
`
`
`Moreover, it is preferred to dissolve the first intennediate
`
`
`
`
`
`
`compound in a solution and elute this solution to purify the
`
`
`
`
`
`
`
`
`first intermediate compound before deprotecting at C7 and
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`C10 and at the C3’ nitrogen site. Here, also, the step of
`
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`replacing the C7 and C10 carbobenzyloxy groups with
`hydrogen is conducted first to produce an amine after which
`
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`
`Page 3
`
`

`
`5
`
`-continued
`
`Reaction I
`
`
`PhCH2OCO2
`
`
`5,688,977
`
`
`
`OCO2CH2Ph 5
`
`
`6
`
`
`
`
`
`
`
`
`
`
`extracted with methylene chloride or ethyl acetate, as
`
`
`
`
`
`
`
`
`desired. The organic layer is separated, dried and reduced
`
`
`
`
`
`
`
`
`under vacuum to residue. The residue was then recrystal-
`lized from ethyl acetate:hexane to result in N—CBZ
`
`
`
`
`
`
`
`
`
`
`
`3-phenylisoserine ethyl ester.
`
`
`
`
`
`
`
`This intermediate was next protected by the hydrogena-
`
`
`
`
`
`
`
`table benzyl-type protecting group in several ways. For
`
`
`
`
`
`
`
`example. one route to the desired hydrogenatable benzyl-
`type protected side chain is as follows:
`
`
`
`
`
`
`
`Reaction 1]]
`
`
`0
`
`
`
`Ph/\ O/u\{GI
`
`
`
`/-\/ CO7'Et E-gLui..i—Cl
`
`THF, -78 C.
`3
`OH
`
`
`
`
`
`
`
`
`
`
`
`0
`Ph/'\ OJL Em
`
`
`Ph/\/ C0zEt
`E)BoM
`
`
`Reaction III
`
`
`10
`
`
`
`20
`
`
`
`25
`
`
`
`30
`
`
` olllllll%
`
`Reaction I
`
`
`
`
`
`
`Here, 10-deacetylbaccatin I[[ is dissolved in anhydrous
`
`
`
`
`
`
`
`THF (tetrahydrofuran) and is cooled under a nitrogen atmo-
`
`
`
`
`
`
`
`sphae to a temperature of less than —20° C. but preferably
`
`
`
`
`
`
`
`—78° C. n-butyl lithium (1.6M in hexane) is added dropwise
`
`
`
`
`
`
`
`
`
`and the solution is stirred at the reduced temperature for
`
`
`
`
`
`
`
`
`approximately five minutes. At least 1.5 equivalents of
`
`
`
`
`
`
`
`
`n-butyl lithium are needed to get significant product yield,
`
`
`
`
`
`
`however 2 equivalents are preferable. Benzyl chloroformate
`
`
`
`
`
`
`
`
`
`is then added dropwise (again, at least 1.5 equivalents of the
`
`
`
`
`
`
`
`
`benzyl chloroforrnate are needed for significant yield, but 2
`equivalents are preferred) and the mixture is stirred over a
`
`
`
`
`
`
`
`
`period of one hour during which time it is allowed to warm
`
`
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`
`
`
`
`
`to a temperature of no more than 0° C. The mixture is then
`
`
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`
`
`
`quenched with cold saturated ammonium chloride to elirni-
`
`
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`
`
`
`
`
`
`
`
`
`
`
`
`
`nate any excess n-butyl lithium and acetyl chloride, and the
`
`
`
`
`
`
`
`mixture is reduced under vacuum. The residue is taken up in
`ethyl acetate and washed once with water and then with
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`brine to remove unwanted salts. The organic layer may then
`
`
`
`
`
`
`
`
`
`
`be dried and reduced under vacuum, and the residue recrys-
`
`
`
`
`
`
`
`tallized or column chromotagraphed with ethyl acetate!
`
`
`
`
`
`
`hexane to yield C7, C10 di-CBZ 10-deacetylbaccatin Ifl as
`
`
`
`
`
`
`
`
`a white solid in greater than 80% overall yield.
`
`35
`
`
`
`
`
`
`
`Here, the hydrogenable benzyl-type protecting group is
`
`
`
`
`
`
`benzyloxyrnethyl (BOM). To prepare this compound, the
`
`
`
`
`
`
`N—CBZ 3-phenylisoserine ethyl ester is dissolved in anhy-
`drous THF under a nitrogen atmosphere and cooled to a
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`reduced temperature such as —40° C. or -78° C., for
`
`
`
`
`
`
`example, in a dry ice/acetone bath followed by the dropwise
`
`
`
`
`
`
`
`addition of an alkyllithiurn agent such as n-butyl lithium,
`
`
`
`
`
`
`
`
`although it is desirable that the alkyllithium agent be a
`straight chain alkyl. In any event, the reaction is best done
`
`
`
`
`
`
`
`
`
`at a temperature no greater than 0° C. The resulting mixture
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`is stirred for about ten minutes. Benzyloxyrnethyl chloride
`(BOM-C1) is then added dropwise over an interval of about
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`five minutes and the mixture stirred for approximately two
`to five hours at the reduced temperature. Thereafter, the
`
`
`
`
`
`
`
`
`solution is warmed to 0° C. and quenched with water to
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`eliminate excess n-butyl lithium. The resulting mixture is
`reduced under vacuum to residue, and this residue is there-
`
`
`
`
`
`
`
`
`after takeu up in ethyl acetate and washed with water and
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`brine to remove unwanted salts. The organic layer may then
`
`
`
`
`
`
`
`
`
`
`be dried and reduced under vacuum and the residue recrys-
`
`
`
`
`
`
`tallized from ethyl acetate:hexane or chromatographed with
`ethyl acetate:hexane to give the N—CBZ C2‘-BOM
`
`
`
`
`
`
`
`
`
`
`3-phenylisoserine ethyl ester.
`Another route to production of N—CBZ C2’-OBOM
`
`
`
`
`
`
`
`
`
`
`
`
`3-phenylisoserine ethyl ester is accomplished by dissolving
`
`
`
`
`
`the compound N—CBZ (2R,3S)-3-phenylisoserine ethyl
`
`
`
`
`
`
`ester in anhydrous methylene chloride. Thereafter, a tertiary
`
`
`
`
`
`
`amine base such as diisopropylethylarnine is added along
`with BOM-C1 and the mix is refluxed for twenty-four hours.
`
`
`
`
`
`
`While this reaction route will produce N—CBZ 2'-BOM-3-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`phenylisoserine ethyl ester, the reaction proceeds much
`more slowly than the route discussed above. However, it
`
`
`
`
`
`
`
`
`may be preferred because of higher yield. Here, the com-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`pound is not purified, but rather is carried on to subsequent
`processing steps in crude form.
`
`
`
`
`In either instance, the resulting N—CBZ C2’-OBOM
`
`
`
`
`
`
`
`
`
`
`
`
`
`(2R,3S)-3-phenylisoserine ethyl ester, either in the purified
`form of the first route or in the crude form from the second
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`B. Production of the 3—Phenylisoserine Side Chain
`
`
`
`
`
`
`
`
`
`
`
`The production of the (2R,3S) N—CBZ C2‘ O-protected
`
`
`
`
`
`
`
`
`3-phenylisoserine ethyl ester side chain, where the C2’
`
`
`
`
`
`hydroxy group is protected by a hydrogenatable benzyl-type
`
`
`
`
`
`protecting group (Formula 2) can be accomplished from the
`
`
`
`
`
`
`
`starting compound (2R, 3S) 3-phenylisoserine ethyl ester
`according to the following two reactions. The first reaction
`
`
`
`
`
`
`
`
`rs:
`
`
`45
`
`
`
`Reaction II
`
`
`2
`
`
`
`m
`1
`CBZ—C1
`
`
`
`
`p1K\( C023‘: NazCO3
`Et O: H O
`3
`
`
`OH
`2
`2
`
`
`
`
`/\
`
`Ph
`
`
`i
`
`
`
`0
`El“
`'
`
`Ph/\/ CO7]-It
`
`on
`
`
`50
`
`
`
`55
`
`
`Reaction II
`
`Here, (2R, 3S) 3-phenylisoserine ethyl ester was alterna-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`tively dissolved in either equal parts diethyl etherzwater or
`equal parts methyl t-butyl etherzwater and the solution was
`
`
`
`
`
`
`
`
`
`cooled to 0° C. The sodium carbonate was then added to the
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`solution and benzylchloroformate was added dropwise over
`
`
`
`
`
`
`
`
`
`an interval of about five minutes and the resulting mixture
`stirred at 0° C. for approximately one hour. After the one
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`hour stirring, the solution was then poured into water and
`
`65
`
`
`Page 4
`
`Page 4
`
`

`
`
`
`
`
`
`
`
`
`route, may simply be converted to the corresponding acid by
`the reaction:
`
`
`
`7
`
`5,688,977
`
`
`
`Reaction IV
`
`
`0
`
`
`
`Ph/\ OJLgm2
`
`
`LiOH
`
`
`
`
`ph/\/ C013 EtOl-Izl-I20 5
`630M
`
`
`
`
`0
`ph/\O/IL I-{H
`
`
`
`Ph/\/ C0211
`E)BoM
`
`
`Reaction IV
`
`
`5
`
`10
`
`
`
`20
`
`
`
`8
`
`-continued
`
`Reaction V
`
`
`
`
`O
`Ph/\ OJLI-in
`
`
`Ph/$/ C02JEt
`z)Bn
`
`
`Reaction V
`
`
`
`
`
`
`
`
`Here, the CBZ protected (2R,3S)-3-phenylisoserine ethyl
`ester is dissolved in anhydrous TI-IF under a nitrogen atmo-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`sphere and cooled to a reduced temperature such as —40° C.
`or —78° C. for example in a dry ice/acetone bath followed by
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`the dropwise addition of an allcyllithium agent such as
`
`
`
`
`
`
`
`n-butyl lithium, although it is desirable that the alkyllithium
`
`
`
`
`
`
`
`agent be a straight chain alkyl. The resulting mixture is
`stirred for about ten minutes. Benzyl bromide (BnBr) is then
`
`
`
`
`
`
`
`
`
`added dropwise over an interval of about five minutes and
`
`
`
`
`
`
`
`
`the mixture stirred for approximately two to five hours at the
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`reduced temperature. Thereafter, the solution is warmed to
`
`
`
`
`
`
`
`
`
`0° C. and quenched with water to destroy excess n-butyl
`lithium. The resulting mixture is reduced under vacuum to
`
`
`
`
`
`
`
`residue, and this residue is thereafter taken up in ethyl
`
`
`
`
`
`
`
`
`acetate and washed with water to remove any lithium
`
`
`
`
`
`
`
`
`bromide salt; it is then further washed with brine. The
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`organic layer may the be dried and reduced under vacuum
`
`
`
`
`
`
`
`and the residue recrystallized from ethyl acetate:hexane or
`
`
`
`
`
`
`chromatographed with ethyl acetatezhexane to give
`
`
`
`
`
`N—CBZ 2'-benzyl 3-phenylisoserine ethyl ester.
`
`
`
`
`Alternatively, the N—CBZ 2'-benzyl 3-phenylisoserine
`
`
`
`
`
`
`
`ethyl ester may be obtained according to the reaction:
`Reaction VI
`
`
`
`
`
`
`30
`
`35
`
`
`
`
`
`
`
`
`
`
`Here, the protected ethyl ester is dissolved in ethanol!
`
`
`
`
`
`
`
`
`
`water (ratio 8:1). Lithium hydroxide (or other suitable alkali
`
`
`
`
`
`
`
`
`hydroxide) is added to the solution and the resulting mixture
`
`
`
`
`
`
`
`
`stirred for approximately three hours in order to saponify the
`
`
`
`
`
`
`
`compound. The mixture is then acidified (1N hydrochloric
`
`
`
`
`
`
`
`
`
`acid) and extracted with ethyl acetate. The resulting organic
`
`
`
`
`
`
`
`
`layer is separated, dried and reduced under vacuum The
`residue acid is then isolated for use without further purifi-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`cation. This produces the desired N—CBZ C2‘-OBOM
`
`(2R3S)-3-phenylisoserine.
`Where the N—CBZ C2‘-OBOM 3-phenylisoserine ethyl
`
`
`
`
`
`ester is carried forward in the crude form and is converted
`
`
`
`
`
`
`
`
`into N—CBZ C2‘-OBOM (2R,3S)-3-phenylisoserine, it is
`
`
`
`
`
`
`
`
`
`
`
`
`
`necessary for further purification of the end product. This
`
`
`
`
`
`purification is accomplished by dissolving the product in
`toluene followed by the dropwise addition of one equivalent
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`of dicyclohexylamine and the resulting solution is stirred for
`one-half hour. This mixture is then concentrated in vacuo,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`and the resulting residue is recrystallized from ethyl
`acetatezhexane to give the dicyclohexylamine salt of the
`
`
`
`
`
`
`
`
`
`
`
`
`N—CBZ C2‘-OBOM (2R,3S)-3-phenylisoserine. The puri-
`fied N—CBZ C2‘-OBOM (2R,3S)-3-phenylisoserine may
`
`
`
`
`
`
`
`
`
`
`
`then be liberated by dissolving this dicyclohexylamine salt
`
`
`
`
`
`
`
`in methylene chloride or another halogenated solvent fol-
`
`
`
`
`
`
`
`
`lowed by washing the methylene chloride with several
`
`
`
`
`
`
`
`
`portions of 1N HCl. The organic layer is then washed with
`
`
`
`
`
`
`several portions of water to remove dicyclohexylamine
`
`
`
`
`
`
`
`
`hydrochloride. Next,
`it is washed with one portion of
`saturated brine and reduced in vacuo to give the desired acid.
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Benzyl itself is another example of a hydrogenatable
`
`
`
`
`
`
`
`benzyl-type protecting group that may be used instead of
`BOM. N—CBZ 2'-benzyl 3-phenylisoserine ethyl ester was
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`produced as above with the substitution of benzyl bromide
`for BOM—Cl according to the reaction:
`
`
`
`
`
`Reaction V
`
`
`0
`
`
`
`Ph/\ OJL Em:
`
`
`BnBr THF
`
`
`
`
`
`ph/\/ C013‘ — n-BuLi >
`
`
`0 I
`
`
`
`40 Ph/\ 0*gm
`
`
`3
`
`ph/\/ C0713‘
`611
`
`
`45
`
`50
`
`
`
`55
`
`
`
`
`
`
`
`Nfi DMF E
`
`limit
`
`
`
`0
`Ph/\OJLyin
`
`
`
`Ph/'\/ C0213!
`E)Bn
`
`
`Reaction VI
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`Here, to a stirred solution of NaH in anhydrous DMF
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`under nitrogen is added N—CBZ-3-phenylisoserine ethyl
`ester dissolved in DMF over five minutes. The mixture is
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`then stirred at 0° C. for one half hour. Then benzyl bromide
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`(1.1 equivalents) is added dropwise over five minutes and
`the reaction is stirred for two hours. The mixture is then
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`quenched with water to destroy excess sodium hydride.
`Thereafter, either diethyl ether or methyl t-butyl ether is
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`added. The organic layer is then washed with four portions
`of water to remove DMF and sodium bromide. Next, it is
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`washed with brine and then dried and reduced under vacuum
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`to produce N—CBZ C2’-benzyl 3-phenylisoserine ethyl
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`ester may then be readily converted into N—CBZ C2’-
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`benzyl 3-phenylisoserine by the process of Reaction IV
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`Page 5
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`Page 5
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`result in the desired C3’ NCBZ C2‘-OBOM-C7, ClO-d.i-
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`CBZ 10-deacetyl baccatin III of the formula:
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`10
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`PhCH2OCO;
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`O
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`Fcmnula 3
`0C02CI-[2Ph
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`0
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`/\ JL
`Ph
`0
`NH 0
`:
`P11/\:)L o‘
`ptv O\/ 0
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`_
`5
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`Ho
`g
`PIICO2
`OAC
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`O
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`D. Deprotection and Treatment with Di-tert-Butyl
`dicarbonate and Deprotection to Form Dooetaxel
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`The following reaction removes the CBZ protecting
`groups at C7 and C10 and the C3‘ nitrogen side chain site.
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`(Again for clarity, BOM is used here as an example of a C2‘
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`hydrogenatable benzyl-type protecting group):
`Reaction VIII
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`O 0
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`5;<0
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`Pl1C]-I;OCOz
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`C02CH2Ph
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`5,688,977
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`45
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`50
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`55
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`60
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`Reaction VIII
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`The coupled product of Formula 3 is dissolved in
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`isopropanol/ethyl acetate to which Pearlman’s catalyst is
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`added. The resulting mixture is hydrogenated at 1 atmo-
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`sphere of hydrogen for at
`least
`twenty-four hours.
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`Thereafter, the mixture is filtered through diatomaceous
`earth and reduced under vacuum to residue to result in the
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`amine shown which is used without further purification.
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`65
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`Next, the t-BOC group can be attached at the N-C3‘ side
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`chain site according to the following reaction:
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`Page 6
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`above with the understanding that, in this case, benzyl is the
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`C2‘ protecting group instead of benzyloxymethyl (BOM).
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`9
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`C. Esterification of the Protected Baccatin III with
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`the Side Chain '
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`Esterification of the C7, C10 di-CBZ 10-deacetylbaccatin
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`III with the N—CBZ C2’-protected 3-phenylisoserine side
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`chain (where the C2‘ hydroxyl is protected by any hydro- ‘
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`genatable benzyl-type group) is accomplished as follows.
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`The preferred hydrogenatable benzyl group shown below is
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`BOM (benzyloxymethyl).
`Reaction VII
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`0
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`10
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`15
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`Ph/\OJL1-SH:
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`C
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`Ph/\=/ 02“
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`PK/O\/O
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`DIPC/DMAP
`tong]:
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`20
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`PhCH;OCOg
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`0 R
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`eaction VII
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`Here, the C7, C10 di-CBZ 10-deacetylbaccatin III (1
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`equivalent) of Formula 1 and the acid side chain (6
`equivalents) of Formula 2 are dissolved in toluene. To 1:his
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`mixture, 4-dimethylamino pyridine (DMAP)
`(one
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`equivalent) and diisopropylcarbodiimide (6 equivalents) are
`added, and the resulting mixture heated at about 60° to 80°
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`C. for one to five hours. It should also be noted, however,
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`that other dialkylcarbodiimides may be substituted for the
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`diisopropylcarbodiimide, with one example being dicyclo-
`hexylcarbodiimide.
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`‘The solution is then allowed to cool to room temperature,
`and next an equal volume of diethyl ether is added. The
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`resulting solution is cooled to 0° C. and held at this tem-
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`perature for twenty-four hours. This step crystallizes most of
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