____________________ COMMUNICATIONS
`
`otides in length. In vitro "evolution" was done on this region at
`30% mutagenesis. and four more rounds of in vitro selection
`followed before this second population was cloned. From these
`sequences, a consensus region was discovered. Certainly though
`this work is a pioneering achievement in the field, it is an ex(cid:173)
`ample of how the conventional protocol is significantly more
`involved than that presented here.
`In summary, a novel in vitro selection protocol has been de(cid:173)
`signed to take advantage of a combinatorial library of small size
`that has multiple copies of every distinct sequence. The method
`condensed the many days of a typical screening strategy to less
`than two days. This was a proof-of-concept experiment that
`showed that the new method succeeds by creating a large num(cid:173)
`ber of copies of individual sequences in the initial random pool,
`consistently reducing the level of nonspecific binding sequences
`per selection round, and effectively amplifying the few surviving
`sequences.
`Since only the original synthesized sequences were used for all
`the screenings, the technique should allow for the iterative
`in vitro selection of modified oligonucleotides that previously
`could not undergo this powerful processJ101 Hence, this method
`should significantly increase the power of the in vitro selection
`method and is the direction that we are currently investigating.
`
`Experimental Section
`
`The DNA library[4] (31 mg) was labeled at the 5'-end with [y- 32P]ATP, purified by
`gel chromatography, and suspended in 300 mL of folding buffer (300mM KCI, 5 mM
`MgCl,. 20mM Tris. pH 7.5). After cooling down to room temperature following
`denaturation at 75 C the 32 P-labeled DNA was loaded onto an acetate-agarose
`precolumn (300 f!L), which was attached directly to a 2.5mM ATP-agarose column
`(800 f!L, Sigma). The precolumn was washed with 600 I'L of buffer, and the eluted
`DNA was allowed to equilibrate on the ATP-agarose column for 10 min. The
`precolumn was discarded after a single use as were all subsequent columns. After
`equilibration. the ATP-agarose column was washed with 4 mL of folding buffer to
`elute unbound or weakly bound oligonucleotides. The retained DNA was eluted
`with 3 mL of the ATP elution buffer (5mM ATP in folding buffer) and collected in
`500 f!L fractions.
`In order to perform another round of selection, the ATP had to be removed. Hence,
`the eluted fractions were collected directly into Microcon-3 microcentrifuge devices
`(3000 D cutoff. Am icon). After membrane diafiltration, about 98% of the total
`ATP was removed. The filtered fractions were then pooled, and folding buffer was
`added until a final volume of 10 mL was attained. The concentration of contaminat(cid:173)
`ing ATP concentration was 30iiM for the DNA sample, which was over 80 times
`more dilute than that of the 2.5mM ATP-agarose column. Each cycle of selection
`started with a new set of stacked affinity columns, i.e. a precolumn attached to a
`ligand column. The screening cycles for the ATP aptamers are summarized in
`Table 1.
`The rare-DNA PCR wa> performed as follows: On the last cycle the DNA was
`eluted from the ATP-agarose column with 3 mL of 10mM ATP in 20mM Tris,
`pH 7.5. This last fraction was precipitated twice from ethanol, and the PCR reagents
`(50mM KCI. 8mM MgSO., lOmM (NH 4 ) 2S04 , 20mM Tris, pH 8 8 at 25 'C, 200JLM
`dNTPs. 0.1% Triton X-100, 20 units of Deep Vent (exo-) DNA polymerase, 0.5 fig
`5'-primer. 0.5 ~g 3'-primer) were added. Thermal cycling (94 'C for 45 s; 42 'C for
`90s; 60 C for 45 s: 45 cycles) was done in a microcentrifuge tube that had first been
`irradiated with UV light. A positive control containing a dilute solution ( -20000
`molecules) of a 52-mer. and a negative control containing no DNA also underwent
`the same amplification protocol. Gel electrophoresis after amplification showed
`DNA in all lanes except the negative control.
`
`Received: February 27, 1997 [Z 10170IE]
`German version: Ange>r. Chern. 1997, 109, 1956-1958
`
`Keywords: aptamers · combinatorial chemistry · in vitro selec(cid:173)
`tion · nucleotides · polymerase chain reaction
`
`[1] L. C. Bock, L. C. Griffin, J. A. Latham, E. H. Vermaas, J. J. Toole, Nature
`1992, 335, 564 566; J. R. Lorsch, J. W. Szostak, Biochemistry 1994, 33, 973-
`982; D. Smith. G. P. Kirschenheuter, J. Charlton, D. M. Guidot, J. E. Repine,
`Chern. Bioi. 1995, 2, 741- 750; D. Jellinek, L. S. Green, C. Bell, N. Janjic,
`Biochemistry 1994.33, 10450-·10456; C. Tuerk, S. MacDougal, L. Gold, Proc.
`Nat/. Acud. Sci. USA 1992,89, 6988-6992; C. Tuerk, S. MacDougal-Waugh,
`Gene 1993.137,33 -39: D.P. Bartel, M. L. Zapp, M. R. Green,J. Szostak, Cell
`1991. 67. 529; C. T. Lauhon. J. W. Szostak, J Am. Chern. Soc. 1995, 117,
`
`1246-1257; P. Burgstaller, M. Famulok, Angew. Chern. 1994,33, 1163-1166;
`Angew. Chern. Int. Ed. Engl. 1994,33, 1084-1087; M. Famulok, J. W. Szostak,
`J. Am. Chern. Soc. 1992, 114, 3990-3991; M. Famulok, ibid. 1994, 116, 1698-
`1706; J. G. Connell, M. !llangesekare, M. Varus, Biochemistry 1993,32, 5497;
`M. Sassanfar, J. W Szostak, Nature 1993,364, 550-553: a) M.G. Wallis, U.
`von Ahsen, R. Schroeder, M. Famulok, Chern. Bio/.1995,2. 543-552; b) R. D
`Jenison, S.C. Gill, A. Pardi, B. Polisky, Science 1994, 263, 1425-1429; J. F.
`Milligan, M.D. Matteucci, J. C. Martin, J Med. Chern. 1993. 36,1923-1937;
`J.D. Ecker, S. T.Crooke, Biotechnology 1995, 13, 351-360.
`(2] Some exceptions include 2'-amino- and 2'-fluoro substitutions on sugar (H.
`Aurup, D. M. Williams, F. Eckstein, Biochemistry 1992,31, 9636-9641) and
`1-pentynyl substitution on pyrimidine (J. A. Latham, R. Johnson. J. J. Toole,
`Nucleic Acids Res. 1994,22, 2817-2822).
`(3] D. E. Hmzenga, J. W. Szostak, Biochemistry 1995, 34, 656 665.
`(4] Oligonucleotides were purchased HPLC-purified from Operon. The initial se(cid:173)
`quence was 5'-GAATTCCAGATCTCT-(18N)-GATATCAGGATCCCA-3'.
`The two primers were 5'-GAATTCCAGATCTCT-3' and 5'-TGGGATCCT(cid:173)
`GATATC-3'. These sequences incorporated EooR I and BaroH I digestion en(cid:173)
`zyme restriction sites.
`[5] D. M. Coen in Current Protocols in Molecular Biology (Eds. F. M. Ausubel, R.
`Brent, R. E. Kingston, D. D. Moore, J. G. Seidman, J. A. Smith, K. Struhl),
`Current Protocols, New York, 1994, Chapter 15.4.
`(6] J.P. Katz, E. T. Bodin, D. M. Coen, J Viral. 1990,64. 1690-1694.
`(7] S. A. Kauffman, The Origms of Order: Self Organization and Selection in Evo(cid:173)
`lution, Oxford University Press, New York, 1993. Chapter 3.
`[8] D. H. Freeman, Anal. Chern. 1972,44, 117 -120; B. M. Dunn,!. M. Chaiken.
`Proc. Nat/. Acad. Sci USA 1974, 71, 2382.
`(9] J.P. Hummel, W. J. Dreyer, Biochim. Biophys. Acta 1962, 63, 530.
`(1 OJ Another method for the use of modified nuc!eotides in the 5'-region of a primer
`has been described recently: J. Burmeister, G. von Kiedrowski. A. D. Ellington,
`Angew. Chern. 1997, 109, 1379-1381; Angel<"- Chern. Int. Ed. Engl. 1997, 36,
`1321-1324.
`
`The Synthesis of Enantiopure
`w-Methanoprolines and w-Methanopipecolic
`Acids by a Novel Cyclopropanation Reaction:
`The "Flattening" of Proline**
`Stephen Hanessian, * Ulrich Reinhold, and
`Gabriella Gentile
`
`Proline occupies a prominent pos1t10n in the hierarchy of
`natural amino acid constituents of mammalian proteins.11 l As
`part of a peptidic motif, its unique structure results in secondary
`amide bonds, leading to important conformational and func(cid:173)
`tional consequences.l2I For example, the well-known cis- trans
`isomerism in prolylamides is associated with vitally important
`biological phenomena and functions, such as protein folding,I 31
`hormone regulation,l4 1 recognition,l 5 l and transmembrane sig(cid:173)
`nalingl61 to mention a few. The importance of cis- trans confor(cid:173)
`mational changes is manifested by the role that peptidyl prolyl
`isomerases such as the immunophilins play in immunoregula(cid:173)
`tionJ7l Proline has also figured prominently as a component of
`therapeutic agents,I 8l in drug design,l9l and in probing enzyme
`activity.llOJ
`Conformationally constrained analogues of proline have
`been used extensively in connection with peptidomimetic re(cid:173)
`search.P 11 Although 2,3- and 3,4-methanoprolines have been
`
`[*] Prof. Dr. S. Hanessian, Dr. U. Reinhold, G. Gentile
`Department of Chemistry
`Universite de Montreal
`C. P. 6128, Succ. Centre-ville
`Montreal, QC, H3C 317 (Canada)
`Fax: Int. code +(514)343-5728
`[**] We thank NSERC for generous financial assistance through the Medicinal
`Chemistry Chair program. We thank Dr. Michel Simard for the X-ray analy(cid:173)
`ses. U. R. acknowledges a DFG Research Fellowship from the Deutsche
`Forschungsgemeinschaft. G. G. thanks the University of Siena and the Italian
`C. N. R. for a summer fellowship.
`
`Angew. Chem. Int. Ed. Engl. 1997. 36,,No. 17
`
`<U WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
`
`0570-0833/97/3617-1881 $17.50+.50;0
`
`1881
`
`MYLAN - EXHIBIT 1010
`
`

`

`COMMUNICATIONS ___________________ _
`
`described,[12· 131 the 4,5-methanoprolines are relatively unex(cid:173)
`plored.l141 Furthermore, structural investigations that study the
`consequences of introducing strain and its effects on the config(cid:173)
`uration and stability of amide linkages are not available to com(cid:173)
`pare such systems to their proline counterparts.
`We describe herein highly stereocontrolled syntheses of the
`diastereomeric 4,5-methano-L-prolines and 5,6-methano-L(cid:173)
`pipecolic acids by a novel intramolecular cyclopropanation re(cid:173)
`action of iminium ions and the extension of the methodology to
`other congeners.[15· 161
`Treatment of the readily available lactam 1 [17•1 with lithium
`hexamethyldisilazide (LiHMDS) and Me3SnCH 2l gave the cx(cid:173)
`alkylated products 2 ([a]0 = -15.3, c = 0.43 in CHCI 3 ) and 3
`([cx] 0 = -16.0, c =1.23 in CHC! 3 ) in 63% and 23% yields, re(cid:173)
`spectively (Scheme 1). The syn-isomer 3 could be easily obtained
`
`LiHMDS, THF
`~ -78°C, then
`0......-.,!~{_f Me,SnCH2l
`Boc OR -30°C
`
`""'J,~M~So~
`
`Boc OR
`
`Boc OR
`
`Table 1. Selected torsion angles and root-mean-square deviations from fitted atoms
`in a given plane ofX-ray crystal structures, and 13C NMR chemical shifts (CDC\ 3).
`
`N-Boc-L-proline !20)
`
`6
`
`8
`
`r(Nc.J
`r(C.C~)
`r(C~C,)
`r(C,C,)
`r(C,N)
`r(BocNC.CO,H)
`rms deviation
`of fitted atoms
`
`-17
`+31
`-35
`+24
`-4
`-72
`0.018
`C., N, C,, C,
`
`-5.6
`+4.8
`-2.6
`-0.7
`+4.1
`-64.0
`0.003
`C~, C,, C,, N
`
`-14.4
`+15.3
`-11.4
`+2.9
`+7.6
`-67.1
`0.013
`c,, C,,C,, N
`
`1
`R=TBDPS
`
`2,63%
`
`74%
`
`3,23% •
`
`1. liHMDS, THF
`2. 2,6-di-tert-butyfphenol, -78°C
`
`S(cis/trans)
`
`o(cis/trans)
`
`o(cis/trans)
`
`178.35/176.60
`153.951155.39
`58.8
`30.75/29.53
`
`177.7(175.5
`157.11154
`60.8(60.1
`32.0
`
`179.1(176.1
`155.7(154.1
`59.5(59.1
`31.5129.1
`
`COOH
`NC=O
`c.
`c,
`RuCJ3, Na104 ~
`"'"/)__
`····-....~~-~ CC!JCH3CN/H20
`~oc OR --7-5.-Yo---;~
`
`Scheme 1. TBDPS = t-BuPh,Si, TFA = tritluoroacetic acid, Boc = tert-butox.y(cid:173)
`carbonyl, CSA = camphor-10-su!fonic acid.
`
`by treatment of the enolate from 2 with the proton source 2,6-di(cid:173)
`tert-butylphenoiY8·191 Generation of the hemiaminal from 2
`and treatment with TFA led to the (4R,5R)-methanopyrrolidine
`derivative 4 ([cx]0 = - 69.3, c = 1.41 in CHC1 3), which was
`smoothly deprotected to 5, and the latter oxidized to give the
`crystalline (4R,5R)-methano-N-Boc-L-proline in excellent over(cid:173)
`all yield.
`Similar treatment of the syn-isomer 3 gave the diastereomeric
`crystalline acid 8 via its methylaminal derivative 7. The struc(cid:173)
`tures and conformations of6 and 8 in the solid state were unam(cid:173)
`biguously confirmed by single-crystal X-ray analysis. Table 1
`lists selected torsion angles for compounds 6 and 8, where con(cid:173)
`siderable "flattening" of the pyrrolidine ring is observed relative
`to N-Boc-L-proline,f2°l particularly in the case of 6. The flatten(cid:173)
`ing of the pyrrolidine ring in 6 is also manifested in the root(cid:173)
`mean-square value of0.003 A for the Cp and N atoms from the
`plane defined by C ,CY,C15 , and N (0.013 A in 8). The lowest
`deviation of0.018 A in the case of N-Boc proline was found for
`c. and C atoms in the plane c.,N,C~,C,; in this case Cp was
`distincti/above the plane (0.521 A). This differs substantially
`
`1. allyiMgCI, THF, -78°C
`
`2. TFA, CH2CI2 ~ Boc OTBDPS
`
`50%
`
`11
`
`2
`
`Scheme 2.
`
`with allylmagnesium chloride, followed by trifluoroacetic acid
`(TFA), led to the (S)-5-(2-propenyl)-4,5-methano-L-proline
`derivative 11 ([cx]0 = - 27.0, c = 0.57 in CHC1 3 ) on migration
`of the double bond. Compounds 10 and 11 represent uniquely
`functionalized precursors to constrained w-methanoprolines.
`The versatility and generality of the intramolecular carbo(cid:173)
`cyclization
`reaction with appended
`trimethylstannylalkyl
`groups via incipient iminium ions can be demonstrated in the
`synthesis of bicyclic proline congeners (Scheme 3). These com(cid:173)
`pounds are related to the antihypertensive agent ramiprii.l2 11 A
`highly stereoselective allylation of the enolate from 1 gave 12
`([cx] 0 =- 45.0, c = 1.0 in CHC1 3), which was subjected to a
`photoinduced trimethylstannylation [221 to give 13 ([ct10 = - 23.6,
`
`1882
`
`© WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
`
`0570-0833197/%17-1882$ 17.50+ .5010
`
`Angew. Chern. Int. Ed. Engl. 1997,36, No. 17
`
`oc
`
`6
`m.p.133-134•C
`[a]o = -200.0
`(c = 1.0inCHCI3)
`
`oc
`
`8
`m.p.12B-129·c
`[a]o =-9.7
`(c = 1.0 in CHCI3)
`
`1. LiEt3BH, THF
`2. TFA, CH2CI2
`2 -......,-:66:::-%:-,-.4---
`+14%,5
`Bu.NF, THF, 90% 14 (R = TBDPS)
`t...S(R=H)
`
`3-
`
`MeO
`
`7
`
`from 6 and 8, in which the out-of-plane carbon atom was the one
`bearing the carboxyl group (0.082 A and 0.235 A respectively).
`Intermediates 2 and 3 could also be subjected to further stereo(cid:173)
`controlled branching leading to the cx-C-allyl derivative 9, which
`upon controlled reduction and acid-catalyzed destannyl(cid:173)
`ation led to the branched 4,5-methano-L-proline precursor 10
`1.UEt3BH, THF MeaSn~ 1. TFA, CH2CI2 ~
`([cx]0 = + 4.3°, c = 0.72 in CHCI 3 ; Scheme 2). Treatment of 2
`2. MeOH, CSA
`(79%)
`3 3. Bu
`, ,..,.Na-10-4-1, ~
`NF/AcOH
`2-.-R-uC-1
`N
`4
`Boc OH CCIJCH,CN/
`THF 83°!.
`H20(71%)
`•
`
`1. liHMDS, THF ~:fi,··· SnMe
`
`2. allyl bromide
`
`'
`
`3
`
`1. liEt3BH, THF
`2. TFA, CH2Cl2
`
`2,3
`
`57%
`
`R = TBDPS
`
`O
`
`N
`Boc OR
`9, trans/cis >20: 1
`
`62%
`
`L
`
`Vt Boc OR
`
`10
`
`

`

`____________________ COMMUNICATIONS
`
`'L
`.J-\...._
`1. LiHMDS,THF
`2. allyl bromide
`----8-1-%--~· o~~~--,
`Boc OR
`12, trans/cis >40: 1
`
`'
`
`Me3SnH
`hv
`
`98%
`
`R=TBDPS
`
`Me3Sn-+,)3
`
`0~ Boc OR
`
`13
`
`1. LiEt3BH, THF
`2. TFA, CH2CI2
`3. Bu4NF, THF
`
`72%
`
`Scheme 3.
`
`(~:I\_ CrD,/H2SO•
`'~~--,
`Soc OH
`
`83%
`
`14
`
`15
`
`c = 0.92 in CHC1 3 ). Formation of the hemiaminal, followed by
`acid-catalyzed cyclization and deprotection, led to the bicyclic
`prolinol derivative 14 ([1X] 0 = - 97.3, c = 1.38 in CHC1 3). Final(cid:173)
`ly, oxidation under Jones conditions gave the immediate precur(cid:173)
`sor to the N-Boc-(4R,5R)-ramipril diastereomer 15 (m.p. 61-
`63 oc; [1X] 0 = -126.7, c = 0.46 in CHC1 3 ).
`It is also of interest to view compounds 6, 8, 10, and 11 as
`precursors to constrained analogues or precursors to L-pipecolic
`acid. The extension of the cyclopropanation reaction to the
`pipecolic acid series is shown in Scheme 4. Trimethylstannyl(cid:173)
`methylation of the lithium enolate derived from the readily
`available 17[231 gave the anti-isomer 18. Reduction to the hemi(cid:173)
`aminal and acid-catalyzed cyclization led to 20 ([1X]0 = - 56.0,
`c = 1.02 in CHCI 3), which was deprotected and oxidized to
`the crystalline (5R,6S)-methano-N-Boc-L-pipecolic acid 21
`(m.p. 138-140 oc; [1X]0 = -105.2, c = 1.17 in CHC13). Epimer-
`
`1. TBDPSCI
`2. Boc20
`
`78%
`
`L liEt3BH, THF
`2.p-ToiS03H
`CH2CI:1/Me0H
`
`16
`
`SnMe3
`
`0~ OH
`~--.. 0
`
`?--~~
`OR
`18, trans/cis =14:1
`
`0~ 1.UHMDS, THF, -78°C
`
`2. Me3SnCH21, -20°C
`
`77%
`
`OR
`
`17
`R=TBDPS
`
`1. Bu4NF, THF
`2. RuCI3, Nal04
`..... ~ ~,,,,
`CCI4/CH3CN/H20
`N
`Boc
`
`65%
`
`OR
`
`ization of 18 to the syn-isomer 19 by diastereoselective protona(cid:173)
`tion, followed by functional group manipulation as described
`above, led to the crystalline diastereomeric (5S,6S)-methano-N(cid:173)
`Boc-pipecolic acid 23 (m.p. 79-81 oc; [1X]0 = -126.7°, c = 0.40
`in CHC1 3 ). The structure of crystalline 21 was unambiguously
`established by X-ray analysis. It is of interest to note that while
`the proline derivatives 6 and 8 adopt a cis-N-Boc proline orien(cid:173)
`tation in the solid state (Table 1), the corresponding 4,5-
`methanopipecolic acid analogue 21 exhibits a trans orientation
`(Scheme 4). The presence of cis and trans isomers of 6 and 8 in
`CDC1 3 was evidenced by the corresponding 13C NMR shifts, as
`in the case of N-Boc-L-proline (Table 1).
`Pipecolic acid is an important constituent of the immunosup(cid:173)
`pressive agents FK-506[ 241 and rapamycin,[ 251 in which its IX-ke(cid:173)
`toamide portion is intimately involved in an "active complex"
`with the target enzymeJ2 6l It is also involved in the metabolism
`of L-lysine, an essential amino acid for mammalian growth and
`development.[ 27 l Functionalized pipecolic acids are also consid(cid:173)
`ered strained analogues of lysine with applications in drug de(cid:173)
`sign and peptidomimetic research,l2 81 as well as in the inhibition
`of L-pipecolate oxidase. [2 71
`It is our belief that the replacement ofL-proline and L-pipecol(cid:173)
`ic acid by conformationally altered ring variants represented by
`the methano congeners described in this work could have im(cid:173)
`portant consequences in biological recognition, in cis- trans
`conformational changes, in the susceptibility of the secondary
`amide bonds to enzymatic cleavage, and in related processes or
`phenomena. Studies that address these issues will be reported in
`due course.
`
`Received: February 4, 1997 [Z 100761E]
`German version: Angew. Chern. 1997, 109, 1953-1956
`
`Keywords: amino acids · asymmetric synthesis · cyclizations ·
`strained molecules
`
`[1 J Example: T. E. Creighton, Proteins. Structures and M olecu/ar Principles, W H.
`Freeman, New York, 1984.
`[2] a) C. M. Deber, V. Madison, E. R. Blout, Ace. Chern. Res. 1976, 9, 1 06-113;
`b) E. S. Eberhardt, S. N. Loh, R. T. Raines, Tetrahedron Lett. 1993, 34, 3055-
`3059; c) W A. Houry H. A. Scheraga, Biochemistry 1996.35,11719-11733.
`[3] a) J. F. Brandts, H R. Halvorson, M. Brennan, Biochemistry 1975, 14, 4953-
`4963; for more recent references see b) K. L. Borden, F. M. Richards, ibid.
`1990, 29, 3071-3077; c) F. L. Texter, D. B. Spencer, R. Rosenstein, C. R.
`Matthews, ibid. 1992,31, 5687-5695; d) K. Lang, F. X. Schmid, J. Mol. Bioi.
`1990, 212, 185-196.
`[4] a) K. A. Williams, C. M. Deber, Biochemistry 1991,30, 8919-8923; b)J. Wess,
`S. Nanavati, Z. Vogel, R. Maggio, R. EMBO J. 1993, 12. 331-338; c) T. M.
`Suchyna, L. X. Xu, F. Gao, C. R. Fourtner, B. J. Nicholson, Nature 1993, 365,
`847-849.
`[5] N. G. I. Richards, M.G. Hinds, D. M. Brennand, M. J. Glennie, J. M. Welsh,
`J. A. Robinson, Biochem. Pharmacal. 1990,40,119-123.
`[6] a) A. Yaron, F. Naider, F. Crit. Rev. Biochem. Mol. Bioi. 1993, 28, 31-81; b)
`R. E. London, J. M. Stewart, J. R. Cann, Biochem. Pharmacal. 1990, 40, 41-
`48.
`[7] a) C. J. Andres, T. L. Macdonald, T. D. Ocain, D. Longhi. J. Org. Chern. 1993,
`58, 6609; b) M. K. Rosen, S. L. Schreiber, Angew. Chern. 1992, 104, 413-439;
`Angew. Chern. Int. Ed. Engl. 1992, 31, 384-400; c) G. Fischer, ibid. 1994, 106,
`1479-1501 and 1994,33, 1415-1436.
`[8] D. W Cushman, H. S. Cheung, E. F. Sabo, M.A. Ondetti, Biochemistry 1977,
`16, 5484-5491.
`[9] M. J. Genin, R. K. Mishra, R. L. Johnson, J. Med. Chern. 1993,36, 3481-3483.
`[10] J. T. Yli-Kauhaluoma, J. T.; J. A. Ashley, C.-H. L. Lo, J. Coakley, P. Wirsching,
`K. D. Janda, J. Am. Chern. Soc. 1996, 118, 5496-5497.
`[11] A. Giannis, T. Kolter, Angew. Chem. 1993, 105, I 303- I 325; Angew. Chem. Int.
`Ed. Engl. 1993, 32, 1244-1267; M. Kahn, Synlett, 1993, 821-826; Peptide
`Secondary Structure Mimetics, Tetrahedron Symposium-in-Print, No. 50 (Ed.:
`M. Kahn), 1993, 49, 3433-3689; J. Gante, Angew. Chem 1994, 106, 1780-
`1802; Angew. Int. Ed. Engl. 1994, 33, 1699-1720; A. E. P. Adang, P. H. H.
`Hermkens, J. T. M. Linders, H. C. J. Ottenheijm, C. J. van Staveren, Reel. Trav.
`Chim. Pays Bas 1994, 113, 63-78; see also, T. Curran. P.M. McEnaney,
`Tetrahedron Lett. 1995,36, I91-194; G. Muller, M. Gurrath, M. Kurz, H.
`Kessler, Proteins: Struct., Funct. and Genet. 1993, 15, 235; S. Hanessian, G.
`McNaughton-Smith, H.-G. Lombart, W D. Lubell, Tetrahedron, in press.
`
`=
`
`21, m.p. 138-140°C
`[a]0 = -105.2 (c = 1.18 in CHCI3)
`
`1. UHMDS, THF, -78°C
`2. 2,6-di-tert-butylphenol
`-100°C
`
`18
`
`92%
`
`1. LiEt3BH, THF
`2. MeOH,CSA
`3. Bu4NFfAcOH, THF
`
`83%
`
`~ OR
`M~~ 1. p-ToiS03H, MeOHI
`
`19, trans/cis= 19:1
`
`CH2CI2 (42%)
`
`2. RuCI3 , Nai04,CCIJ
`CH3CNfH20 (60%)
`
`23, m.p. 79-81•C
`[a]0 = +126.7 (c = 0.4 in CHCI3)
`
`y"'~~
`22
`
`OH
`
`Scheme 4.
`
`Angew. Chern. Int. Ed. Engl. 1997, 36, No. 17
`
`© W!LEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
`
`0570-0833/97/3617-1883 $17.50+ .50/0
`
`1883
`
`

`

`COMMUNICATIONS ____________________ _
`
`1,8-Bis( dimethylamino )-4,5-dihydroxy(cid:173)
`naphthalene, a Neutral, Intramolecularly
`Protonated "Proton Sponge" with
`Zwitterionic Structure**
`Heinz A. Staab,* Claus Krieger, Gisela Hieber, and
`Klaus Oberdorf
`
`The interaction of basic groups in close proximity to each
`other may lead, as in the case of 1,8-bis(dimethylamino)(cid:173)
`naphthalene (1), to unusually high basicities ("proton spon(cid:173)
`ges").111 The influences of gradually changed distances and ori(cid:173)
`entations of the basic centers as well as of inductive, mesomeric,
`and steric effects on the basicity of such compounds have been
`thoroughly studiedJ21 In comparison to the basicity of 1
`[pK. ~ 12.1 (H 20); 7.5 (DMSO)],f31 that of 2,7-dimethoxy-1,8-
`bis(dimethylamino)naphthalene (2) is found to be increased by
`four powers of ten [pK. ~ 16.1 (H20); 1L5 (DMSO)].l31 To
`separate the mesomeric effect of the two methoxy groups from
`their steric effect on the dimethylamino groups, we were inter(cid:173)
`ested in 3, an isomer of 2 in which the two methoxy groups are
`not in the 2,7-positions but in the opposite peri-positions. In
`fact, 1 ,8-bis( dimethylamino )-4,5-dimethoxynaphthalene (3) is
`considerably less basic [pK. ~ 13.9 (H 20); 9.3 (DMSO)] than
`the isomer 2, indicating that the main reason for the high basic(cid:173)
`ity of 2 is the steric effect of the methoxy groups in ortho-posi(cid:173)
`tions to the dimethylamino groups. Irrespective of this primarily
`intended basicity comparison of 2 and 3, the synthesis of 3
`should allow the easy preparation of the corresponding 4,5-di(cid:173)
`hydroxy compound 5, which by intramolecular proton displace(cid:173)
`ment may lead to a new type of neutral, yet zwitterionic "proton
`sponge" (formula 6).
`
`Mo~s2 Me2N
`
`fi
`
`MeOroOMe
`::,.,1 &
`
`NMe2 "(;¢~
`
`fi
`
`[12] Synthesis of racemic and enantiopure 2,3-methanoproline: a) A. Hercouet, B.
`Bessieres, M. Le Corre, Tetrahedron: Asymmetry 1996, 7, 1267 -1268; b) F. L.
`Switzer, H. van Halbeek, E. M. Holt, C. H. Stammer, Tetrahedron 1989, 45,
`6091-6100. Recent accounts on 2,3-methanoamino acids: C. H. Stammer,
`Tetrahedron 1990,46, 2231-2254; K. Burgess, K. K. Ho, D. Moyl-Sherman,
`Synlett 1994, 575-583; K. Burgess, C.-Y. Ke, J. Org. Chern. 1996, 61, 8627-
`8631; J. M. Jimenez, R. M. Ortuno, Tetrahedron: Asymmetry 1996, 7, 3203-
`3208, and references therein.
`[13] Synthesis of cis- and /rans-3,4-methanoprolines: a) Y. Fujimoto, F. Irrevere,
`J. M. Karle, I. L. Karle, B. Witkop, J. Am. Chern. Soc. 1971, 93, 3471-3477;
`recent discussion of cyclopropylpyrrolidines: D. F. Harvey, D. M. Sigano, J.
`Org. Chern. 1996,61, 2268-2272; K. E. Brighty, M. J Castaldi, Synlett 1996,
`1097-1099.
`[14] Synthesis of racemic 4,5-methanoproline amides: a) H. Urbach, R. Henning,
`R. Becker, DE-A 3,324,263 (CI. C07D209/2) [Chern. Abstr. 1985, 103: P
`54461q]; b) related example involving mixtures of diastereomers: R. Pellicia(cid:173)
`ri, L. Arenare, P. De Caprariis, B. Natalin, M. Marinozzi, A. Galli, J. Chern.
`Soc. Perkin Trans. 1 1995, 1251-1257.
`[15] a) S. Hanessian, U. Reinhold, S. Ninkovic, Tetrahedron Lett. 1996,37,8967-
`8970; b) S. Hanessian. S. Ninkovic, U. Reinhold, ibid. 1996, 37, 8971-8974.
`[16] Selected examples of carbocyclizations mediated by alkyltin(Iv) intermediates:
`T. L. Macdonald, C. M. Delahunty, K. Mead, D. E. O'Dell, Tetrahedron Lett.
`1989,30, 1573-1576; T. L. Macdonald, S. Mahalingam, D. E. O'Dell, J. Am.
`Chern. Soc. 1981, 103, 6767-6769; cyclopropane formation from y-stannyl
`alcohols: D. D. Davis, H. T. Johnson ibid. 1974, 96, 7576-7577; H. G. Kuivila,
`N. M. Scarpa, ibid. 1970, 92, 6990-6991; N. Isono, M. Mori, J. Org. Chern.
`1996,61, 7867-7872; cyclopropane formation from {J-stannyl ketones: T. Sa to,
`M. Watanabe, T Watanabe, Y. Onoda, E. Murayama, ibid. 1988, 53, 1894-
`1899; C. R. Johnson, J. F. Kadow, ibid. 1987,52, 1493-1500.
`[17] a) S. Hanessian, G. McNaughton-Smith, Bioorg. Med. Chern. Lett. 1996, 6,
`1657-1662; see also b) S. Saijo, M. Wada, J.-I. Himizu, A. Ishida, Chern.
`Pharm. Bull. 18, 28, 1449; c) T. Katoh, Y. Nagata, Y. Kobayashi, K. Arai, J.
`Minami, S. Terashima, Tetrahedron Lett. 1993, 34, 5473-5476; d) K.-H. Alt(cid:173)
`mann, ibid. 1993, 34, 7721-7724. e) J. Ackermann, M. Matthes, C. Tamm,
`Helv. Chim. Acta 1990, 73, 122-132.
`[18] S. G. Davies, N. M. Garrido, O.!chihara, I. A. S. Walters, J. Chern. Soc. Chern.
`Commun. 1993, 1153-1159.
`[19] All new compounds afforded satisfactory spectroscopic and analytical data
`('H, 13C NMR, IR, LRMS, HRMS). Experimental procedures are available
`upon request. Crystallographic data (excluding structure factors) for the struc(cid:173)
`ture reported in this paper have been deposited with the Cambridge Crystallo(cid:173)
`graphic Data Centre as supplementary publication no. CCDC-100227. Copies
`of the data can be obtained free of charge on application to The Director,
`CCDC, 12 Union Road, CambridgeCB21EZ, UK (fax: int. code +(1223)336-
`033; e-mail: deposit@chemcrys.cam.ac.uk).
`[20] E. Benedetti, M. R. Ciajolo, A. Maisto, Acta Crystallogr. Sect. B 1974, 30,
`1783-1788.
`[21] a) V. Teetz, R. Geiger, R. Henning, H. Urbach, Arzneim.-Forsch./Drug Res.
`1984, JOb, 1399; b) R. Henning, U. Lerch, H. Urbach, Synthesis 1989,265-268
`and references therein.
`[22] Hydrostannylation of alkenes: M. Lautens, S. Kumanovic, C. Meyer, Angew.
`Chern. 1996, 108, 1428-1429; Angew. Chern. Int. Ed. Engl. 1996, 108, 1428-
`1431, and references therein.
`[23] a) S.-B. Huang, J. S. Nelson D. D. Weller, Synth. Comm. 1989,19, 3485-3496;
`b) S. A. Hermitage, M.G. Moloney, Tetrahedron. Asymmetry 1994, 5, 1463-
`1464.
`[24] J J. Sierkierka, S. K. Y. Hung, M. Roe, C. S. Lm, N.H. Sigal, Nature 1989,341,
`755-757.
`[25] a) M. W Harding A. Galat, D. E. Uehling, S. L. Schreiber, Nature 1989,341,
`758-760; b) H. Fretz, M. W Albers, A. Gala!, R. F. Standaert, W S. Lane, S. J.
`Burakoff, B. E. Bierer, S. L. Schreiber, J. Am. Chern. Soc. 1991, 113, 1409-
`1410.
`[26] J. Liu, J.D. Farmer, W. S. Lane, J. Friedman, L. Weissman, S. L. Schreiber,
`Cell 1991, 66, 807-815.
`[27] T. M. Zabriskie, J. Med. Chern. 1996, 39, 3046-3048, and references therein.
`[28] P. J. Murray, I. D. Starkey, Tetrahedron Lett. 1996,37, 1875-1878; A. Claes(cid:173)
`son, B.-M. Swahn, K. M. Edvinsson, H. Molin, M. Sandberg, Bioorg. Med.
`Chern. Lett. 1992, 2, 1247-1250.
`
`Me2 ~NMe2 ·os "(;D~
`~ &
`
`2
`
`, .. H .. ,
`
`&
`
`MeO OMe
`
`HO
`
`OH
`
`MeO OMe
`3
`
`... H·.,
`
`&
`-.....
`e
`Q,,H_.{)
`
`4
`
`5
`
`6
`
`For the synthesis of 3, 1,8-dihydroxynaphthalener4 J was
`methylated to give 1,8-dimethoxynaphthalene, which was ni(cid:173)
`trated (cone. nitric acid, glacial acetic acid/dichloromethane,
`9: 5)
`to yield 1 ,8-dimethoxy-4,5-dinitronaphthalene (39%;
`m.p. 278 °C); the isomeric 2,5-dinitro product (m.p. 151-
`153 oq was separated by chromatography on silica gel with
`dichloromethane as eluent. Catalytic hydrogenation (10% Pd/
`C, tetrahydrofuran (THF), 20 oq resulted in the formation of
`1 ,8-diamino-4,5-dimethoxynaphthalene (97%; m.p. 83-95 °C,
`decomp), which was N-methylated according to the method of
`Quast et aJ.f 5l to give 3 (71%; m.p. 75 °C, from n-hexanejethyl
`
`[*] Prof. Dr. H. A. Staab, C. Krieger, Dr. G. Hieber, Dr. K. Oberdorf
`Abteilung Organische Chemie
`Max-Pianck-!nstitut fiir medizinische Forschung
`Jahnstrasse 29, D-69120 Heidelberg (Germany)
`Fax: Int.code +(6221)486219
`e-mail: staab@mixi.mpimf-heidelberg.mpg.de
`[**] New "Proton Sponges", Part 12. Part 11: H. A. Staab, M. Diehm, C. Krieger,
`Tetrahedron Lett. 1996, 36, 2967-2970.
`
`1884
`
`© WILEY -VCH Verlag GmbH, D-69451 Weinheim, 1997
`
`0570-0833/97/3617-1884 $ 17.50 + .50/0
`
`Angew. Chem. Int. Ed. Engl. 1997,36, No. 17
`
`