EXHIBIT NO. J}.
`
`P. Antone, CRR
`
`Inr. J. P:-pride Pr-nm'n Res. 32. I988. 279-291
`
`Synthesis of functionalized non-natural amino acid derivatives via
`
`amidoalkylation transformations
`
`PHILIPPE LEGALL“. KAILASH N. SAW]-INEY. JUDITH D. CONLEY and HAROLD KOHN
`
`Department of Chemistry, University of Houston. Houston, TX, USA
`
`Received 16 February. accepted for publication 2 May I988
`
`Synthetic routes have been developed for the preparation of functionalized amino
`acid derivatives in which the wsubstitucnt at carbon 2 is either an aromatic or a
`
`hcteroaromatie group. The oz-substituent was introduced using an amidoalkylation
`reaction using boron trifiuoride etherale and proceeded in moderate yield with
`excellent regioselectivity. This protocol permitted the employment of the acid sen-
`sitive heterocycles: pyrrole. benzofuran. and indole. The scope and limitations of this
`procedure have been evaluated.
`
`Key words: at-substituted: amido alkylation transformations; aromatic; heteroaromatic; non-
`natural amino acids
`
`Recent studies conducted in our laboratory
`have drawn attention to the importance of
`-at-functionalized derivatives of N-acetylgly—
`eine—N-benzylamide (1, R = H) as potential
`drug candidates for the treatment of epilepsy
`(I).
`in an efibrt
`to delineate the structure
`activity relationship ofthis novel class of anti-
`convulsants, select derivatives of l were re-
`quired in which the a-substituent R was either
`an aromatic or a heteroaromatic moiety. Un-
`fortunately, relatively few methods exist for
`the preparation of the corresponding free
`amino acids“ thereby diminishing the likeli-
`hood of employing these substrates as start-
`
`‘/tbstracted from the Masters dissertation of
`
`this
`
`author. Additional structure proofand experimental and
`spectra data may be found in this reference.
`
`“The 2- and 3-thienyl compounds are commercially
`available (Aldrich Chemical Company). For leading ref-
`erences for procedures for the preparation ofnon-natural
`amino acides and related studies. see ref. 2.
`
`ing materials for the synthesis of I. In this
`paper, we describe the use and limitations of
`amidoalkylation transformations“‘* for the
`preparation of functionalized derivatives of
`amino acids in which the R substituent is an
`
`aromatic moiety.
`
`'i“i
`II
`cH,cNHt|:c NHCI-l,Ph
`H
`
`1
`
`RESULTS AND DISCUSSION
`
`Two diflerent strategies (Scheme l, Methods
`A and B) were investigated for the prepara-
`tion of I. The approaches differ primarily in
`the sequence of reactions employed for the
`synthesis of the desired compound I.
`In
`
`*“‘ For excellent discussions of this reaction. see ref, 3.
`
`279
`
`DEF_0000632
`
`MYLAN - EXHIBIT 1104.13
`
`MYLAN - EXHIBIT 1104.13
`
`

`
`P. LeGall M (II.
`
`the initial target was the 2-stth-
`Method .-’\.
`stituted alkyl 2-acetamidoacetate 6. Our syn-
`thesis of this compound was patterned after
`the procedure described by Ben-lshai. Sataty
`& Bernstein for the preparation of methyl
`.-'\"-benzyloxycarbonyl-1—furanglycinate
`(2).
`Reaction oh1cetztn1idc(2} \\ itlt glyoxylic acid
`(3) yielded -4 in near qtiantitativc yield (4).
`which upon dissoltttion in either methanol or
`ethanol and acid gave the corresponding
`alkyl 2-acetantido-_-alkoxyacetates 5a and
`Sb. Treatment of 5 with either
`furan or
`
`pyrrole in the presence of boron trifiuoride
`ctherate gave the 1-substituted product 6 in
`moderate yield (5l—()2".-a).
`In the case of
`furan. only 63 was observed in which sub-
`stitution had occurred at the 2—position of the
`arontatic ring. Correspondingly. with pyrrolc
`a 3.4:l binary mixture of the aromatic 3(6c, )-
`and 3(6c;)- substituted compounds. respec-
`tively. was obtained. Unliortttnately. attempts
`to convert 6 to the corresponding benzyl
`amide adduct
`I proved uttsatisfttctor_\_'. Low
`yields were obtained for the condensation of
`benzylamitie with 6. Similarly. unacceptable
`overall yields for I were experienced for the
`sequential conversion of 6 to the acid 7
`lK0H- H20). followed by the coupling of the
`N-protected amino acid 7 with benzylaniine
`li.e.. ClC03R. ELN: DCC)‘.
`This synthetic obstacle was expeditiously
`circumvented by the use of
`the
`second
`pathway (Method Bl outlined in Scheme I. In
`this procedure.
`the coupling reaction was
`conducted prior
`to
`the arnidoalkylation
`transformation. Treatment of alkyl 2—aceta-
`niido-2-alkoxyacctates
`Sn
`and
`5b with
`benzylaminc in alcoholic solution produced
`the corresponding 3—acetan1ido-N-henzyl-L
`alkoxyacetamidcs 8a and 8b.
`respectively.
`Higher yields and cleaner product mixtures
`were noted for the synthesis oFetho.\ty adduet
`8b versus the methoxy derivative 82:. Corn-
`pound 8b was converted to I by treatment
`with the appropriate aromatic or hetero-
`
`
`The direct C0n\'t:rSIOn N11 to 7 was hriefiy ex-antined (-1).
`Adtlitton of either
`lurtut or henzoltiran to 4 in the
`Prcscttce of Le» is acids yieldeti the corresponding z-sub-
`sllllllflhl ammo acid Llt.‘Tl\'.|ll\'t‘.\ in ion yields t|4—2t_)".,)_
`Fill‘ Ltddilittttttl details, see llmtmitc‘
`
`280
`
`aromatic substrate and boron trifluoride
`
`ctherate. This synthetic route permitted the
`preparation of compounds la-ll. Moderate
`yields (2S~‘)='l%) for this step were observed
`for
`l‘ur-an.
`2-mcth_vll‘ur-an.
`pyrrolc.
`l-
`methylpyrrole.
`thiuphene. benzofuran.
`indole. phenol, p-cre.<.oI. anisole and thin-
`phenol. while only a -l"’o yield was Obtained
`for benzo[b]thiophcne (Table I). Employ-
`ment of pyrazole. imitiazole. pyridine, 3- and
`cl-ltydroxypyridine.
`benzene. naphthalene.
`and N-acetylaniline as the aromatic substrate
`in this procedure led to no detectable product
`forittation. No significant effort was made to
`vary either the acid or the solvent employed
`in the amidoalkylation step in order
`to
`improve the efficiency of this transformation.
`Several interesting observations were noted
`concerning the conversion of the 2—ethoxy
`derivative 8|: to 1. First. the employed con-
`ditions (boron trifluoride ctheratc. ether) per-
`mitted the use of the acid sensitive hetero-
`
`cyclcs: pyrrole. benzofuran. and indole. These
`substrates have found limited use in previous
`amidoalkylation translbrmations. (Zaugg (3).
`S. 6). Second. in the reaction of pyrrolc only
`it trace amount of the 3—substitutcd pyrrole
`product was detected tt.l.c. analysis). A much
`larger percentage of
`the
`corresponding
`adduct was observed when ester 5b was em»
`
`ployed as the starting material (Scheme I.
`Method A). The high regioselectivity wit-
`nessed in the former transformation was also
`mirrored in the other reactions with hetero-
`
`aromatic substrates. Typically. only one
`isomer was observed. This result was par-
`ticularly surprising in the reactions involving
`benzofuran and ht.-nzo[b]thiophcne. With
`benzofuran only the 2-substituted aromatic
`derivative was observed despite the known
`tendency of
`this heterocycle to undergo
`alkylation at both the 2- and 3-positions ('7).
`while with benzo[b]thiophenc none of the ex-
`pected
`3-substitutetl
`henzolblthiophene
`product was observed (7) but rather only a
`4% yield of the 2—substitutcd adduct was
`isolated along with urtreactcd starting mat-
`erial. Third. all four substituted benzene sub-
`
`strates (phenol. p-cresol. anisolc. and thio-
`phenol) reacted to give a single product (t.l.c.
`analysis). In the case of phenol and anisolc
`
`DEF_00O0633
`
`

`
`Funetionalized non-natural amino acid derivatives
`
`TABLE I
`
`591,-1-1;-d p.ll'_1'.s'i('a/ and spectral data for 2-ztremmirlo-N-ben:_r!-2-.1ub5ritmed (l('PI:lnlld(‘3' ( U
`
`,1: 1,...VQ;
`CH,
`1111 3
`,.
`1
`
`
`No.
`
`R
`
`Yield“
`M.p.“
`M‘,.'c'
`‘H n.m.r."
`'-‘C n.m.r.‘
`:11-CH
`:1-(‘
`
`
`1
`
`11:
`
`1c.
`
`1.1
`
`De
`
`1:
`
`lg
`
`‘,1
`
`’
`
`“,_;'[§'_
`
`.‘&:1):.
`H
`L
`,('N‘)".
`511,
`\’
`‘,1
`‘ 54‘1'
`I
`
`*
`I
`
`‘
`
`" {I
`11‘
`,
`‘
`ta
`1 x’,
`1 ta ta‘
`3
`4
`
`511
`
`61
`
`35
`
`62
`
`37
`
`33
`
`211
`
`111 5 4
`
`I
`
`-1 In
`
`I
`
`’
`
`178-179
`
`27311)’
`
`5.50111. 7.91
`
`511.95
`
`|48—l50
`
`174-175
`
`179-131
`
`286(3)
`
`271 (12)
`
`235 1171
`
`5.49 (d. 11.01
`
`5.42 (d. 5.911
`
`5.52 (d. 7.31
`
`l67—I69
`
`289 121'
`
`5.74111. 7.9)
`
`195-196
`
`32215)
`
`5.77111. 8.11
`
`213-214
`
`.121 (51
`
`5.72111. 7.21
`
`226-227
`
`252-235
`
`333 (8)
`
`299(1)‘
`
`5.86 (d. 3.11
`
`5.34td. 7.41
`
`195-1912
`
`313 121‘
`
`5.42 (d, 7.31
`
`183-185
`
`31317)’
`
`5.63 to. 7.51
`
`I65 I67
`
`315 (l)'
`
`5.90 (d, 9.0)
`
`53.2.1
`
`52.65‘
`
`49.211
`
`52.20
`
`51.22
`
`49.911
`
`52.711
`
`55.90
`
`55.73
`
`51.54
`
`57.65
`
`11
`
`1j
`
`111
`
`“°‘/'
`
`-
`
`I
`c"'°@
`5
`I
`ms
`I $1
`
`'
`
`OH
`
`t‘ f :4-
`
`
`ll
`
`56
`
`152
`
`67
`
`94
`
`"Purified yields ("/5) from 2-acetamid0-N-benzyl-2-elhoxyacetamide (8b). " Melting points (‘'0 are uncorrected. " The
`molecular ion peak in the mass spectrum was obtained at an ionizing voltage of 'I0ev. The number in the parentheses
`indicates the relative intensity of this ion relative to the base peak in the spectrum. ‘The 300 MHz ‘H n.m.r. spectra
`were taken in DMSO-d‘, unless otherwise indicated. The number in each entry is the chemical shift value (6) observed
`in parts per million relative to TMS. The information in parentheses is the multiplicity of the signal, followed by the
`coupling constant (J) in Hertz. ‘The 75 MHz "C 11.m.r. spectra were taken in DMSO-d,, unless otherwise indicated.
`The number in each entry is the chemical shift value in parts per million relative to TMS. ‘ The M —'—
`1 peak was
`observed [McLalTcrty, F.W. "Interpretation of Mass Spectra." 2nd edn., WA. Benjamin: Reading. MA.
`I973).
`'*N.m.r. spectrum was taken in CD_.CN.
`
`281
`
`DEF_0000634
`
`

`
`P. LeGa|l et at‘.
`
`5*
`°
`cmiiunccoon’
`J‘
`
`RH
`BF3.Et20
`
`6
`
`A
`
`——>
`
`t
`it
`cH,CN|-ICCOOH
`L
`
`7
`
`\
`
`:1 R = 2- Furan
`c,R = 2- Pyrrole
`r- R = 1- Pyrrole
`
`RH
`8F3.Et20
`
`‘f
`if
`CH,CNH¢;.CONHcH,Ph
`H
`
`1
`
`,,-R —.- 2 Furan. R = CH,
`(wk = 2- Furan. R’ = C‘H:CH_-
`<',R = 2- Pyrrole. R’ = (‘H.CH.
`.-,R = 3 Pyrrolc. R‘ = <:H.c H.
`
`5
`
`I
`
`(‘JR
`R
`cH,c umlzcouucmpn
`
`H s
`
`u R’ = C“,
`b R’ = CH_.CH_.
`
`3
`
`‘it?
`at
`cH'cNH_ . HCCOH —-p
`
`?“'
`it
`2°"
`it
`cu,cuHrl:cooH ....> cn,cuHccooR'
`H
`H
`
`2
`
`3
`
`4
`
`SCHEME I
`
`s
`= (.
`
`U
`
`” R" = ‘” C”.-
`
`the para-substituted adducts 1i and 1], respec-
`tively, were observed. while with p-cresol only
`II: was isolated in which reaction had oc-
`
`curred orrh0- to the phenolic group. Finally,
`sulfur rather than carbon substitution was
`
`in the
`observed with thiophenol. Fourth,
`reaction involving indole, the indoie trimer 9
`(8) was obtained along with the desired
`product
`lg.
`lndole is known to undergo
`trimerization in the presence of both mineral
`and Lewis acids (8. 9}.
`
`
`
`spectral properties were
`Characteristic
`noted for the newly prepared functionalized
`amino acid derivatives 1 in agreement with
`the proposed structural assignments (l0, ll).
`In particular. the chemical shift value for the
`at-carbon proton ranged from 65.34 to 5.90 in
`the 'H n.m.r. spectra. while the correspond-
`ing methine carbon signal appeared between
`49.20 and 57.65 ppm. Evidence
`for
`the
`proposed site of aromatic substitution was
`secured from both the ‘H and "C n.m.r.
`spectra. In each case.
`the proton chemical
`shift values as well as the proton-proton
`coupling patterns were in excellent agreement
`with previously reported compounds of com-
`parable substitution patterns (8, 12). More-
`over. in the "C n.m.r. spectra, the chemical
`shift values observed for the substituted aro-
`
`matic carbon atoms were always downfield
`[6.0—-20.0 ppm) versus
`the corresponding
`signal in the unsubstituted heterocycle (1 1).
`In several cases (compounds 1i and lk) the
`"C n.m.r. assignments were aided by per-
`
`DEF_00O0635
`
`

`
`Functionaiized non—natural amino acid derivatives
`
`forming the corresponding APT n.m.r. ex-
`periment (13).
`
`CONCLUSIONS
`
`A facile procedure has been developed for the
`synthesis of non-natural amino acid deriva-
`tives containing an electron-rich aromatic or
`heteroaromatic at-substituent using an amido-
`alkylation transformation. The
`reaction
`proceeded with high regioselectivity and per-
`mitted the use of the acid sensitive hetero-
`cyclesz pyrrolc, benzofuran, and indole. Sig-
`nificantly. this approach should be applicable
`for the preparation of peptides in which the
`peptide bond is formed prior to the introduc-
`tion of the aromatic or heteroaromatic sub-
`
`strate. Optimization of the general reaction
`conditions (i.e,. Lewis acid, solvent) should
`allow the synthesis of other or-substituted
`functionalized amino acid derivatives.
`
`EXPERIMENTAL PROCEDURES
`
`General methods
`
`Melting points were determined with a
`Thomas-Hoover melting point apparatus and
`are uncorrected. Infrared spectra (i_r.) were
`run on either a Perkin-Elmer 1330 or a
`
`Perkin-Elmer 283 spectrophotometer and
`calibrated against
`the l60lcm“ band of
`polystyrene. Absorption values are expressed
`in wavenumbers (cm*'). Proton (‘H n.m.r..
`300MHz) and carbon (“C n.m.r,. 75 MHz)
`nuclear magnetic resonance spectra were
`taken on either a Nicolet NT-300 or a
`
`General Electric QE300 instrument. Chemi-
`cal shifts are in parts per million (6 values)
`relative
`to tetramethylsilane (TMS) and
`coupling constants (J values) are in Hertz.
`Mass spectra were performed at the Eli Lilly
`Corporation, Indianapolis, Indiana, or by
`Dr. John Chinn at the Department of Chem-
`istry. University of Texas at Austin. Elemen-
`tal analyses were conducted at the Eli Lilly
`Corporation, Indianapolis, Indiana. Acetoni-
`trile and triethylamine were distilled from
`Cam; and tetrahydrofuran and ethyl ether
`were distilled from Na/benzophenone.
`Furan, pyrrolc, benzofuran, ethyl chloro-
`fomiate, and isobutyl chloroformate were
`fractionally distilled prior to use. All other
`
`chemicals were ofthe highest grade available
`and were used without further purification.
`The mixed anhydride reactions as well as the
`amidoalkylation transformations using
`boron tn'l’luon’de etherate were run under
`
`In these cases. all
`anhydrous conditions.
`glassware was flame-dried under N2. the solid
`starting materials were dried in vacuo prior to
`use. and the reactions were conducted under
`
`a positive pressure of N2. Preparative flash
`column chromatography was
`run using
`Merck silica gel, grade 60. 230-240 mesh, 60
`A from Aldrich Chemical Company,
`Milwaukee, Wisconsin. Thin-layer chromato-
`graphic analyses were run on precoated silica
`G microscope slides (2.5 x 10cm; Analtcch
`No. 01521) or on precoated silica GHLF mi-
`croscope slides (10 X 20cm; Analtech No.
`21521).
`
`Preparation of methyl
`2-acetamido—2-methoxyacerate (5a)
`Sulfuric acid (95%, 4mL, 70 mmol) was
`added to a methanolic solution (230 mL) of
`2-aoetamido-2-hydroxyacetic
`acid
`(4)
`(4)
`(13.30 g, 100 mmol). The solution was stirred
`at room temperature (48 h), neutralized with
`solid Nai-ICO3. filtered. and then the metha-
`nol was removed in vacuo. The pink oil was
`distilled under vacuum (70—120°, 0.6 torr) to
`give a colorless oil which was recrystallized
`from petroleum ether (35—60°) to yield 5.20g
`(32%) of the desired product: R,-0.52 (9822
`chloroform/methanol); m.p.
`44-4-6°;
`i.r.
`(KBr) 3270, 2820. 1735, |650(br). 1505, 1205,
`1110. 1090. 1010. 930. 900cm‘ '; ‘H n.m.r.
`(CDC1,) 62.08 (s, CH,C0), 3.46 (s, 0CH,),
`3.81 (s, COOCHJ), 5.54 (d. J = 9.3 Hz. CH),
`6.70-6.80 (br d, NH); ”C n.m.r. (CDCl_.)
`22.98 (CH3CO), 52.69 (COOCI-1,), 56.48
`(CH30), 78.16 (CH),
`168.49
`(CH3C0).
`l70.67 (COOCI-l,)ppm; mass spectrum, m_/"e
`(relative intensity) 162 (1), 146 (2), 131 (3).
`118 (3). 102 (46), 88 (25), 60 (100).
`Anal. calc. for C,,H,,NO4: C 44.72. H 6.88, N
`8.69. Found: C 44.46, H 7.14, N 8.72.
`
`Preparation of ethyl
`2-at-examido-2-ethoxyacetate (5b)
`Sulfuric acid (95%, 8mL.
`l40mmol) was
`added to an ice cold ethanolic solution
`
`283
`
`DEF_O00O636
`
`

`
`P. LeGall er al.
`
`2—acetamido-2-hydroxyucetic
`of
`(500mL)
`acid (4) (4) (26.6 g. 200mmo1). and the solu-
`tion was stirred at room temperature for 72 h.
`The yellow colored solution W115 cooled (1)-
`5°) and neutralized with a cold aqueous sat-
`urated NaHCO_. solution (400mL). The re-
`sulting mixture was extracted with ethyl
`acetate (3 x 500m1.). The organic layers
`were combined and the volatile materials
`
`removed in \‘¢7('ll(). The remaining yellow
`liquid was extracted with ethyl
`acetate
`(500mL) and the extract dried (Na3SO,,) and
`evaporated to dryness in 1‘{l(‘Mn. The oily
`residue was purified by distillation under
`vacuum (70—95°. 0.3-0.8 torr) to give 21 .04g
`(55%) of a white waxy solid: R,0.53 (9822
`chloroform/methanol): m.p.
`3S—36°:
`i.r.
`(l(Br) 3400 (br). 1735. 1655 (br). 1200. 1085
`(br). 1010.930. 890cm" :11-1' n.m.r. (CDC|_:l
`61.23 (t. J = 7.31-12. OCH_.CH_-_). 1.32 (t.
`J-_—
`7.3 Hz. OCH3CH_.l. 2.08 (s. CH_.CO).
`3.70
`(q. J = 7.3 Hz. OCH_.CH_.). 4.25 (q.
`J:
`7.3 Hz.
`CO0CH3CH_.).
`5.60
`(d.
`J1
`9.6Hz. CH). 6.96 (br d. J : 9.6Hz.
`NH): "C n.m.r. (CDCl_.) 13.78 (O(‘H,CH_-.).
`14.75 (0CH_.CH_i). 22.91 (CH_-.CO). 61.74
`(COOCH;CH_.1. 64.72 l0Cl-l;CH-.). 76.85
`(CH). 168.25 ((71-LCO). 170.48 (CO0CH3-
`CH,)ppm; mass spectrum. m.-‘e (relative in-
`tensity) 190(5). 160(2). 14408). l16(98). 102
`(92). 74 (100); high resolution mass spectrum.
`calc.
`for C,.H.,,NO.
`190.1079.
`found
`190.1087.
`
`Preparation of alk_t'I-s'ub.m'tuted-so
`a('eIamid0aCeIare.s (6 _/
`
`General’ procedure. The alkyl 2-acetamido-2-
`alkoxyacetate (S) (1 equiv.) was suspended in
`anhydrous ethyl ether (60mL.'l0mmo1). and
`then boron trifluoride etherate (l.6equiv.)
`was added in one portion followed by the
`hcterocycle (4 equiv.) The solution was
`stirred at room temperature (72 h) and then
`poured into an ice~cold saturated aqueous
`solution of Nal-1C‘Oi.
`stirred at
`ice tem-
`
`perature (20min). and then extracted with
`ethyl acetate (3 x) method. The organic
`layers were combined. dried (Na:S0,,). and
`concentrated to dryness in ramp. The result-
`ing oil was purified by flash chromatography
`or recrystallization.
`
`284
`
`Data for all new compounds prepared by
`this technique are listed below.
`
`Mctlryl at-rtceraniidii—3:_iirrunat'erute ( 6a j. The
`desired compound was purilied in 62% yield
`by flash chromatography (99:l chloroform/'
`methanol): R,-0.32 (99:1 ehIoroform,«‘metha-
`no1);m.p. 80~-81°: i.r. (KBr) 3200, 1740. 1620
`(br).
`1530 (pr).
`1205.
`1090.
`1020. 900,
`890cm '1
`‘Hn.m.r.
`(Cl)Cl3)
`52.03
`(s.
`CH_.C0). 3.75 (5. 00-13). 5.77 (d, J =
`7.8 Hz. CH). 6.35-6.36 (m. C,H. C411). 7.02
`(d. J = 7.3 Hz. NH). 7.36 (br s. C_.H); "C
`n.m.r.
`(CDCl3l
`23.69
`(CH,CO).
`50.43
`l0CH_:). 52.88 (CH).
`108.72 (C,), 110.78
`(C4).
`142.84
`(C5).
`148.89
`(C2).
`169.57
`(CH_-.C0). 169.96(C(lOCH3CH_.)ppm;mass
`spectrum. mje (relative intensity) 197 ('14).
`165 (35). 154 (78). 133 (36). 96 (100). 94 (93).
`69 (16).
`Anal. calc. for Cal-1, , N04: C 54.82, H 5.62. N
`7.10. Found: C 54.96. H 5.40. N 7.27.
`
`( 6a’) .
`at-rtrtltuntir/0-Jjizranacelate
`E!/[17
`Compound 63’ was isolated in 51% yield
`after two successive Ilash chromatographies
`((a) 100% chloroform: (b) 70:30 ethyl ether/
`pentane.
`then 97:3 chloroform/methanol):
`R,0.l7 (1009-‘o chloroforrn); m.p. 69—70°; i.r.
`(KBr) 3200. 1750. 163S(br). 1530,1380. 1335,
`1205. 1180. 1020. R90. 745. 595cm ';'H
`n.m.r.
`(CDC1_.)
`61.24
`(t.
`J = 7.2 Hz.
`0CH]CH})~ 2.04 (s. CH_.CO_). 4.14-4.32 (m,
`0CH3CH_.l. 5.75 (d. J = 8.1 Hz. CH), 6.34-
`635 (m. C_.H. QH). 6.35-6.54 (br cl, J =
`8.1 Hz. NH). 7.355.-'..‘~6 (m. CSHJ; "C n.m.r.
`(CDC1_.) 13.91 (OCH;C1-1_._), 22.81 (CHJCOJ.
`50.33 (CH). 62.08 (OCI-13CH_.). 108.49 (C3).
`110.62 (Ci). 142.64 ((..‘_.). 148.85 (C2). 168.89
`(CH.C0'). 169.43 (COOCH,CH_.)ppm: mass
`spectrum. m,'e (relative intensity) 21 1 (8), 168
`(32). 138 (27). 96 (100). 94 ('27).
`Anal. calc. for C.,,H.~.NO,,: C 56.87, H 6.20.
`N 6.63. Found: C 56.98. H 6.19. N 6.83.
`
`Ethyl at-at‘omn1{do-£’—;i_t-rraleatetale (6c, J and
`erlrt '1
`at-at'4'Iam((1043-p_t‘rro1eacera!e
`( 6c_, ).
`T_.1.c. analysis at the conclusion of the reac-
`tion indicated the presence of two major com-
`pounds (R, 0.33 and R, 0.19. 98:2 chlorofomt/"
`methanol). which were isolated by flash chro-
`
`DEF_0000637
`
`

`
`Functionalized non-natural amino acid derivatives
`
`chloroform/methanol).
`(98:2
`matography
`The initial fraction (R,~0.33. 98:2 chlorofonnj
`methanol) was further purified by a second
`flash
`chromatography
`(97:3
`dichloro-
`methane/methanol) to produce 6c,
`in 41%
`yield: m.p. 104-106°; i.r. (KBr) 3310. 3200.
`1715. 1635 (br), 1515 (br), 1220. 1180. 1085,
`1010. 890cm"';'H n.m.r. (DMSO-do) 61.16
`(L1 = 7.21-12. 0CH2CH,). 1.88(s. C1-1_,C0).
`4.01-4.16 (m. OCH2CH3), 5.33 (d, J =
`6.9 Hz. CH). 5.96-5.99 (m_. C311, C414). 6.69-
`6.72 (m, C51-1), 8.48 (d. J = 6.9 Hz, CONH),
`10.80-10.99 (br s. N1-1);
`'-‘C n.m.r. (CDC13)
`13.93 (OCH3CH_.), 22.79 (CH,CO), 50.73
`(CH). 61.38 (OCH3CH_.). 106.35 (C_.)., 107.52
`(C4).
`118.07
`(C_.).
`125.28
`(C3).
`169.24
`(CH3CO], 170.1 1 (C0OCH1CH_,)ppm; mass
`spectrum. m/‘e (relative intensity) 210 (22),
`l67(36), 137(54), l21(7).106(7), 95 (100).93
`(97), 79 (5), 68 (53).
`Ana1.ca|c. for C,.,1-1,4N3O,:C 57.13. H 6.71.
`N 13.33. Found: C 57.20, H 6.55. N 13.13.
`The
`second
`fraction
`(R,0.l9,
`98:2
`chloroform/methanol) was further purified
`by a second flash chromatography (95:5 di-
`chloroniethanefmcthanol) to give 6c; in 12%
`yield: m.p. 92-93°;
`i.r.
`(KBr) 3320, 3240.
`1720. 1640 (br). 1510. 1400 (br). 1210. 1180,
`1010. 890cm": ‘H n.m.r. (CDC1_.) 61.25 (1,
`J = 6.9112. OCHZCH3). 2.02 (s. C1-1_.C0),
`4.10-4.30 (m, OCH:CH})s 5.53 (d, J =
`7.2 Hz. CH), 6.17-6.30 (m. C,,H). 6.25 (d.
`J = 7.2112. CONH), 6.70-6.75 (m. C51-11.
`6.78-6.80 (m, C; H). 8.45-8.60 (br s, NH); ”C
`n.m.r.
`(CDC13) _l3.93 (0CH3CH_.), 22.79
`(CH—.CO). 50.73 (CH). 61.38 (OCH_.CH_.),
`106.78 (C4). 116.56 (C3), 118.25 (C3), 118.63
`(C,). 169.79 (CH,CO). 171.76 (C0OCH3-
`CH-.)PDm: mass spectrum. mic (relative in-
`tensity) 210 (12). 167 (16), 152(5). 137 (31),
`I21 (3). 95(100)._ 93(l0O). 80(5). 68 (71): high
`resolution mass spectrum. ealc. for C,,,1-1,4-
`N_.O_-,210.1004, found 210.1015.
`
`Prepamttbn of .s'ub.s'(iluted
`-at-at-etanzidoaceric acids‘ ( 7 ) from alk_1'!-
`subnilu ted-a-awlalztidoacerates { 6)
`
`(ieneral procedure. The alkyl 2-substituted--av
`aeetamidoacetate (6) (1 equiv.) was dissolved
`in 90:10 ethanol/water (~ 9mL/1 mmol) and
`then KOH (1.1 equiv.) was added and the
`
`room tem-
`resulting solution stirred at
`perature (48 h). The
`reaction was con-
`centrated in varuu and the residue diluted
`
`with H30 and then washed with either ethyl
`acetate or ethyl ether. The aqueous layer was
`then made acidic with 8.5% I-1,PO4 and ex-
`tracted with ethyl acetate (3 x ). The organic
`layers were
`combined. dried (Na,S0..).
`evaporated to dryness in vucuo. and then re-
`crystallized to yield the desired product.
`Data for all new compounds prepared by
`this technique are listed below.
`
`or-Ac-eramido-Zfimmaceric acid (711). Com-
`pound 7a was isolated in 51% yield after
`recrystallization from acctonitrile: R,0.37
`(8:1 :1 isopropanol/N1-1_.0H;'H3O)_; m.p. 171-
`172°; i.r. (KBr) 3320, 3100, 1705. 1580(br).
`1530. 1410. 1360. 1320, 1280, 1270, 1225.
`1210, 1145. 1100. 1010. 890. 660. 640. 610.
`570, 400cm": ‘H n.m.r. (DMSO-db) (51.88
`(s. CH_;CO), 5.45 (d, J = 7.8 Hz, CH). 6.39-
`6.45 (m. C)“, C4111), 7.65 (5. C511). 8.69
`(d, J = 7.8 Hz, NH). [The carboxyl proton
`was not detected] "C n.m.r.
`(DMSO-d,,)
`22.10(CH_-.). 50.16(CH). 108.17(_C.«). 110.66
`(C4).
`142.83
`(C5).
`149.75
`(C3).
`169.21
`(C1-1,670). 170.01 (CO0H)ppm: mass spec-
`trum. m/e (relative intensity) 183(2), 165 ( 10).
`l40(24).123(19),109(1), 96 (100), 94 (43), 80
`(2), 69 (8).
`Anal. calc. for C,.H9NO4: C 52.46, H 4.95. N
`7.65. Found: C 52.61, H 4.93. N 7.94.
`
`at-Aremnrido-2-p_t—'rra1euretic acid (70,). The
`product was
`recrystallized
`(ch1oro1"orm/
`methanol/hexanes) to give 7:, (29% yield):
`R,0.55
`(821: 1
`isopropanol/NH.0H,/H30):
`m.p.
`l12—114°; i.r. (1(Br) 3340, 3300, 1710.
`1590 (br),
`1530 (br).
`1220.
`1080.
`885.
`725cm"';
`'1-1
`n.m.r.
`(DMSO-d6)
`61.87
`(CH3CO). 5.31 (d. J = 7.2 Hz, CH). 5.96
`(S, (.7311). 5.97 (S. C41-11. 6.87 (5. C51-I), 8.40 (d.
`J = 7.2 HLCONH), 10.79-10.85(br 5. NH).
`[The earboxyl proton was not detected.] "C
`n.m.r.
`(DMSO-d,.) 22.16 (CH,CO). 50.45
`(CH),
`106.21
`(C,),
`107.45
`(C,),
`117.83
`(Cs). 126.11 (C3). 169.13 (CH_.CO). 171.56
`(COOH)ppm; mass spectrum. m,-"e (relative
`intensity) 182(1), 164(7). 151 (45), 138 (100).
`137 (25), 121 (2). .95 (98), 93 (10). 91 (46).
`
`285
`
`DEF_0000638
`
`

`
`P. LeG-all at al.
`
`at-Acetamido-3-p_1-rroieaceric (l('fd r7c_.). The
`beige residue was recrystallized (chloroformf
`methanol/hexanes) to Furnish 7c: (38% yield):
`Rf0.28
`(8:l:]
`isopropanol,-"NH,,OH,’H3O):
`m.p. 135—138°; i.r. (KBr) 3340, 3300. 1700.
`1585 (br), 1525 (br). 1240 (br). 920. 895 cm ':
`‘H n.m.r. (DMSO-do) 61.85 (s. CH_..CO). 5.05
`(<1. J = 7.0Hz. CH), 6.04 (s. C,H). 6.69
`(5, C2H), 6.76 (s, C_.H). 8.23 (d, J = 7.0112.
`CONH), 10.68-10.86 (br 5. NH). [The car-
`boxyl proton was not detected.) "C n.m.r.
`(DMSO-d,,) 22.18 (CH-,C0). 50.57 (CH).
`106.98 (C.), 116.28 (C3). 117.33 (C, and
`C5), 169.13 (CH_.C0). 173.00 (COOH) ppm:
`mass spectrum, rn_:e (relative intensity) 182
`(4),164(6), 157(1). 138(100). 124(3). 121
`(38). 95 (19). 93 (33). 80 (94). 68 (91); high
`resolution mass spectrum. calc. for C,,H,,,-
`N30 182.0691. found 182.0688.
`
`Preparation of
`:1-A(-examido-N-benzyl-2Juranact-Iamide
`(Ia)
`1-Acetamido-2-furanacetic acid (72) (0.47 g.
`2.56mmol) was combined with acetonitrile
`(l0mL) and cooled to —5° (ice-‘salt water
`bath). Triethylamine (0.26 g. 0.36 mmol) was
`then rapidly added and the mixture stirred at
`—5°
`(3min). Ethyl chloroformate (0.28 g,
`0.25 mL, 2.56 mmol) was added dropwise
`between -4 and — 3°, and the resulting sus-
`pension was stirred at —4° (20 min). and then
`an acetonitrile solution (2 mL) of hcnzyla-
`mine (0.30 g. 0.31 mL. 2.82 mmol) was care-
`fully added. During the addition of benzyta—
`mine the temperature ofthe solution did not
`go above 0°. The mixture was stirred at — 5°
`(lh) and at room temperature (18 h). and
`then concentrated in ramo. The residue was
`
`tetrahydrofuran
`then triturated with hot
`(5mI..). cooled at -— 16° (3 h). and the result-
`ing white precipitate was filtered and iden-
`tified as
`triethylamine hydrochloride (' H
`n.m.r. analysis). The filtrate was evaporated
`to dryness in racuo and the resulting oil puri-
`fied
`by
`flash
`chromatography
`(9822
`ch1oroform.:'methanol) to give a 13% yield
`(0.09 g) of
`la: R.-0.30 (98:2 chloroform-
`methanol); m.p. 178—l79°;
`i.r. (KBr) 3230.
`1625 (br), 1525 (br). 1375 (br), 1230. 1090.
`890. 740. 690cm'::‘H n.m.r.
`(DMSO-d,,)
`
`286
`
`(51 .90 (5. CH_(C0), 41.31 (d.J = 6.0 Hz, CH3),
`5.58 (d. J = 8.1 Hz. CH). 6.27-6.33 (m,
`C. H), 6.40-6.44 (m. C,H), 7.20-7.36 (m, Ph).
`7.60—7.64 (m. C5H). 8.58 (d, J = 8.lHz,
`NH). 8.73 (t. J = 6.0112. NH); "C n.m.r.
`(DMSO—dh) 22.35 (CH_.C0), 42.27 (CH2).
`50.95 (CH). 107.60 (C3), 110.55 (C4), 126.82
`(2C,. or 2C_..), 127.08 (2C1- or 2C,-), 128.27
`(C, ). 139.05 (C, ). 142.58 (C5), 151.16 (C2).
`168.02 (CH,CO). 169.30 (CONH)ppm; mass
`spectrum. mfe (relative intensity) 273 (1), 230
`(1). 139 (100). 96 (94). 91 (51), 65 (9).
`Anal. calc. for C,_.H,,,N3O,: C 66.16. H 5.83,
`N 10.29. Found: C 65.92, H 5.83, N 10.15.
`
`Preparanbn qf
`2—ac'emmido—N-ben:_rI'-2-methoxyacetamide
`(8a)
`
`To a methanolic solution (180 mL) of methyl
`2—acetamido—2-methoxyacetate (5a)
`(8.73 g,
`54mmo1) was rapidly added benzylamine
`(8.68g. 8.80mL,
`81 mmol) and then the
`mixture was stirred at 50° (3 days) during
`which time a beige precipitate appeared. The
`solvent was removed in vacuo and the result-
`
`ing precipitate was recrystallized from tetra-
`hydroiurun (2 x ) to give 7.67 g (32%) of the
`desired product as beige crystals: R,0.35 (9525
`chloroformfmethaiiol); m.p.
`145—146°;
`i.r.
`(KBr) 3260. 1625 (br). 1550, 1505, 1435, 1390,
`1370.
`1230.
`1 120.
`1060, 935, 890, 740,
`690cm ‘,
`'H n.m.r.
`(CDC13) 62.06 (s.
`CH_,CO). 3.39 (s. CH_,O). 4.35-4.40 (m,
`CH3). 5.52 (d. J = 8.7Hz, CH). 7.12 (d.
`J = 8.7 Hz, NH). 7.20-7.40 (m._ Ph, NH); “C
`n.m.r. (CDCl_,) 23.03 (CHJCO), 43.51 (CH,),
`55.84 (CHJO), 78.94 (CH). 127.62 (C.-).
`127.70 (ZC3 or 2C;-1. 128.70 (2C3. or 2C,.),
`137.45
`(C,-).
`167.01
`(CHJCO).
`171.57
`(CONH)ppm: mass spectrum, m/e (relative
`intensity) 237(1). 205(2). 193 (1), 177(2). 163
`(4).146(1).134(1).121(2),106(26),102(94),
`91 (95). 77 (13). 61 (100).
`Anal. calc. for C,3H,_.,N1O_.: C 61.00. H 6.83.
`N 11.86. Found: C 60.91. H 6.85. N 11.66.
`
`P1't’[)(ll'(l!10fZ of
`2-at'0minido-N—I7¢’r1:_1'/-2-er/t0x_1‘at‘etan1ide
`/85)
`
`An ethanolic solution (420 mL) of ethyl 2-
`acetamido-2-ethoxyacetate
`(Sb)
`(27.92g.
`
`DEF_O00O639
`
`

`
`Functionalized non-natural amino acid derivatives
`
`147 mmol) and benzylamine (23.70 g, 24 mL,
`221 mmol) was stirred at 40—45° for 3 days.
`The reaction mixture was evaporated in vacua
`and the residue recrystallized (3.521 tetrahy-
`drofuran/hexanes [650mL]) to yield 25.8053,
`(70%) of the desired product as beige crystals:
`12,059 (9515 chloroform/methanol); m.p.
`153-155°:
`i.r. (KBr) 3260, 1630 (br). 1550
`(sh). 1505 (br). 1380. 1360. 1230, 1115, 1065,
`1015. 890. 740. 690cm";'H n.m.r. (CDCI3)
`61.20 (t. J = 7.0112, 0CH2CH,). 2.07 (s,
`C.'H_.CO), 3.60-3.76 (m. OCH3CH_,), 4.40-
`4.54 (m. CH3NH), 5.60 (d, J’ = 8.7 Hz, CH),
`6.63 (d, J = 8.7 Hz, NH), 7.00 (br 5. NH),
`7.26-7.36 (tn, Ph); '3C n.m.r. (CDC1_,) 15.06
`(OCl-I2CH_,).
`23.25
`(CH3C0),
`43.60
`(CHZNH), 64.51 (OCHECH3), 77.43 (CH).
`127.69 (ZCZ. or 2C3-, C.-), 128.79 (2C,. or
`2C_.-). 137.57 (C,.), 168.13 (CH3C0). 171.29
`(CONH) ppm; mass spectrum. In/e (relative
`intensity) 251 (4), 163(9), 116 (98), 106 (34),
`91 (98). 74 (_100).
`Anal. calc. for C,3H.,,N,O_.: C 62.38, H 7.25.
`N 11.19. Found: C 62.49, H 7.27, N 11.24.
`
`Preparation of 2-.s'ubsn'mIed
`at-ucetamido-N-bcnzyIat'eIann'des ( I ) from
`2—acetamia'o—N-benzy1—2-ethoxyacetamide
`(3b)
`
`General procedure. 2—Acetamido-N-benzy1-2-
`ethoxyacetamide (8b) (1 equiv.) was suspend-
`ed in anhydrous ethyl ether, and then boron
`trifluoride
`etherate
`(1.6—6.3equiv.) was
`rapidly added and the resulting solution was
`stirred for 15min. The aromatic substrate
`
`(1 6—16equiv.) was then added and the reac-
`tion was stirred at room temperature (1-
`7days). The experimental workup varied
`slightly for each compound and is described
`below along with the observed spectral
`properties.
`
`at-.44emmido-N-henzyi-2-furanucelaniide
`(la). The reaction mixture was poured into
`an ice-cold saturated aqueous solution of
`NaHCO,_, and then stirred at 0° (20 min), and
`then the mixture was extracted with ethyl
`acetate (3 x). The organic layers were com-
`bined, dried (Na,SO,,), and evaporated to
`dryness in vacuo. The product was further
`purified by flash chromatography (70:30 ben-
`
`zenefacetone) to yield the title compound in
`58% yieid as white crystals: Rr0.30 (98:2
`chloroform/methanol); m.p. 178-179“; mixed
`melting point with sample prepared by mixed
`anhydridc method, m.p.
`l78—179°.
`
`at-A cetamido-N -ben::_I-'I-2- ( 5 -methyl]uran ) -
`acetamide (lb). The reaction mixture was
`poured into an aqueous saturated Na}-{C0,
`solution and extracted with ethyl acetate
`(3 x ). The ethyl acetate extracts were com-
`bined, dried (Na,SO..) and evaporated in
`vacuo to give a beige solid. which was purified
`by flash chromatography (98:2 chloroform]
`methanol)
`to yield 61% of the desired
`product as a white crystalline solid: R,0.25
`(98:2 chloroform/methanol); m.p. 148-150°;
`i.r. (KBr) 3270, 1620 (br), 1520 (br), 1440.
`1360, 1210, 1010cm";'H n.m.r. (DMSO-d,_,)
`61.88 (s, C1-l,C0), 2.23 (s, CH3), 4.24-4.36
`(m. CH2). 5.49 (d, J = 8.0 Hz. CH), 6.01 (br
`5. C311). 6.14 (d, J’ = 2.4 Hz, C411), 7.20-7.31
`(111, Ph), 8.52 (d. J = 8.0 Hz. NH). 8.69 (t.
`J = 5.6 Hz, NH);
`"‘C n.m.r.
`(DMSO-d,,)
`13.44 (CH,). 22.35 (CH_.CO), 44.11 (CH3).
`53.23 (CH). 107.51 (C, or C.)_. 110.40 (C; or
`C4). 128.13 (C.-). 128.18 (zc, or 2c_.. ), 129.43
`(2C;r or 2C,.), 139.69 (C.-). 149.18 (C, or C, 1,
`153.81 (C, or C5). 170.78 (_CH,C0). 173.03
`FCONH) ppm; mass spectrum. m/e (relative
`intensity) 286 (3). 179(8). 153 (57). 152 (57).
`I11 (23), 110 (100), 97 (23). 91 (31).
`Anal. calc. for C,.,H,,,N,O_,: C 67.12, H 6.34.
`N 9.78. Found: C 66.92. H 6.52. N 9.52.
`
`at-Acetamido-N-ben:_vl—2-p_i-JrroleaceIamida
`_(Ic,). Hexanes were added to the reaction.
`and the mixture was filtered and the brown
`semi-solid
`was
`triturated
`with
`95:5
`
`to furnish a green
`chloroform/methanol
`solid. This material was purified by flash
`chromatography (95:5 chloroform/methanol)
`to yield the desired product in 35% yield as a
`white solid: R,0.29 (96:4 chloroform/metha-
`nol); m.p. 174-175°‘.
`i.r. (KBr) 3230, 1610
`(br), 1500, 1470 (br), 1330, 1230, 1070, 950.
`890, 860, 740. 710, 685, 655cm '; '1-1 n.m.r.
`(CD_.CN)
`51.93
`(5, CHJCO),
`4.35
`(d.
`J = 6.0 Hz. CH2). 5.42 (cl, J = 6.91-iz, CH).
`6.00-6.18 (m, C311. C,H). 6.68—6.72 (m.
`287
`
`DEF_O000640
`
`

`
`P. LeGa1l 0! ul.
`
`C,-H). 7.04 (d. J = 6.9 Hz. NH). 7.17 (t.
`J = 6.0Hz. NH). 7.i0—7.47 (m. Ph). 9.25--
`9.35 (br 5. NH); '-‘C n.m.r. (CI)_.CN) 22.02
`(CH_.CO), 43.83 (CH3). 52.65 (CH). 107.57
`(C1). 108.85 (C4).
`ll9.33 (C5). 127.96 (C;).
`128.01 (2C3 or 2C,-). 128.09 (2C3 or 2C. ).
`129.49 (C4). 140.01 (C, ). 170.94 (CH.CO).
`171.21 (CONI-I)ppm: mass spectrum.
`in c
`(relative intensity) 271 (12). 228(1). 213(1).
`180(2).164(9).137(94).l08(20).95(100).9l
`(38). 82 (35). 68 (15): high resolution mass
`spectrum. calc.
`for C,_.H,.N.()3 271.1321.
`found 271.1314.
`
`1-Acemmida-N-hm:_i'1-2-1' I-meth_1'ip_i'rro1e/-
`acemmide (Id). The thick brown residue that
`
`deposited during the reaction was separated
`and the ether
`layer was poured into an
`aqueous saturated N-aHCO_. solution. The
`mixture was
`extr