Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

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1.3.2.1 Meophilic Amination The diastereoselective synîhesis of Fhydroxy-a-amino acids €rom epoxides is particularly amenable to nucleophilic amination (Scheme 1.10). The Sharpless epoxidation provides a convenient route to both stereoisomers of the epoxides 1.24 and 1.25 which are subsequently protected as the carbarnate 1.26 and isomerized to the oxazolidinones 1.27 followed by straightforward deprotection to the p-hydroxy-a-amino acids generally in good yields and with high ~iiastereoselectivity.~~ Minor contamination is a result of nonregioselective ring opening of the epoxides 1.26 during oxazolidinones formation. Scheme 1.10 &OH Ri-bkCs D &O&NHR~ NaH ,-D AwR1 1) one es ieagsin 1.24 1.26 R 21 HWmbis NH~ Another route to p-hydroxy-a-arnino acids via epoxy allylic alcohols is by oxidation to the corresponding acid followed by epoxide opening by arnmonia, primary amines and hydrazines which avoid the regioselectivity problems desctibed in Scheme 1.10 since attack is exclusively at C2 (Scheme 1.1 I)? O
O Scheme 1.11 O R1,qH2 m OH RI= H, ~ 0, NHR' Bn, NH2 a-Hydroxy-carboxylates are also readily available chiral compounds and lend themselves to N-nucleophilic substitution (Scheme 1.12). The reactions are generally clean although racemization difficulties have been encountered. Direct substitution by N- nucleophiles has ken achieved with sodium azide," amines:2 phthalimidef3 and imides3) under Mitsunobu conditions. Conversion of the alcohol to the triflate and subsequent direct displacement with di-N-Boc-imide has proven to be especially effective3' and has advantages over the Mitsunobu method, which requires harsh conditions for the unmasking of the nitrogen functionality. Scheme 1.12 One of the best methods for the generation of a-amino acids by nucleophilic amination has been developed by Evans et al? The use of N-acyloxazolidinones 18M to generate a-bromides followed by SN2 displacement to the azide gives the desired precursor in high diastereoselectivity (usuaily 90% de) (Scheme 1.13). Altering the stereochemistry of the N-acyloxazolidinones 18m cm generate both enantiomers of 1.6. Furthemore, P-substituted-a-amino acids have been synthesized by first incorporating
Page 1 and 2: Solution and Solid Phase Synthesis
Page 3 and 4: The University of Waterloo requires
Page 5 and 6: Many people have made the experienc
Page 7 and 8: Table of Contents Abstract ........
Page 9 and 10: 23 Summary ........................
Page 11 and 12: 5.1.4.1 Enzymatic Methods .........
Page 13 and 14: List of Tables Table 2.1 Table 2.2
Page 15 and 16: Figure 4.1 O Figure 5.1 Figure 5.2
Page 17 and 18: CYS d DAST DBAD DBU DCC de DEAD dec
Page 19 and 20: NMP Nu OB0 ester PEG Ph Phe PhFl Ph
Page 21 and 22: 1.1 General Introduction Chapter On
Page 23 and 24: acids will be presented including a
Page 25 and 26: .J generation of the enolate and ad
Page 27 and 28: classical techniques (Scheme 1.7) a
Page 29: s~ccess.~ The same principle has be
Page 33 and 34: stereosele~tivities.~ Numerous exam
Page 35 and 36: Williams and coworlcers have examin
Page 37 and 38: template, reaction with alkyl halid
Page 39 and 40: The 3-bromo analog of Williams and
Page 41 and 42: formation of serine aldehydes; dire
Page 43 and 44: Scheme 1.24 R dimethoxy- R ProPane
Page 45 and 46: of thiol trityl led to racemic cyst
Page 47 and 48: nucleophiles such as acetate and im
Page 49 and 50: may be employed, while the oxidatio
Page 51 and 52: Several methods for the removal of
Page 53 and 54: 1.5 References Barrett, G.C. Chemis
Page 55 and 56: (a) Schmidt, U.; Meyer, R.; Leitenb
Page 57 and 58: R.M. Tetrahedron Le#. 2001,42, 769.
Page 59 and 60: (a) Lubell, W.D.; Rapport, H. J. Am
Page 61 and 62: Nakajima, K.; Takai, F.; Tanaka, T.
Page 63 and 64: 2.1 Introduction Chapter Two Synthe
Page 65 and 66: 2.1.1 Synthesis of SHydroxy-a-Amino
Page 67 and 68: typically generated in both poor yi
Page 69 and 70: 2.1.3.3 Electrophilic%Nucfeophilic
Page 71 and 72: Scheme 2.8 2-(Arylthi0)-2-nitrooxir
Page 73 and 74: Scheme 2.10 Schollkopf et al. have
Page 75 and 76: 2.1.3.5 Synthesis fiom #-Amino Acid
Page 77 and 78: HO Scheme 2.17 This laboratory prev
Page 79 and 80: Scheme 2.19 NaBr, acetone The best
Page 81 and 82:
equires carefiil attention to preve
Page 83 and 84:
order to investigate this as a poss
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etained its optical activity indica
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2.2.3.2 Ortho Ester Cleavage Concom
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2.2.4 Determination of Enantiomeric
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minof si face aîîack mior re face
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2.4.1 General Methods. Most reagent
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The crude product was fiitered thro
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250 MHz) 6 5.47 (br ci, lH, J = S.O
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evaporated to dryness. The residue
Page 101 and 102:
minutes. The akohol solution was tr
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302.1604, found 302.1593; Anai. cal
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CCH3), 28.3 (a3)C), 20.1 (fLm3) 13.
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TLC (4: 1, CH2C12:EtOAc) Rf = 0.44;
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100-200 mesh, hydrogen form, 1x10 c
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(br d. IH. J= 10.6Hz, CHH-CH), 4.63
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mp 80-8 1 OC; [a~~*~a= -67.0 (0 1.5
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esin column (Bio-Rad AGa 10x4 10-20
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Jung, M.E.; Jung, Y.H. Tetruhedron
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(a) Adams, Z.M.; Jackson, R.F.W.; P
Page 121 and 122:
(a) Roemmele, R.C.; Rapport, H. J.
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- - 68. Gawley, R.E.; Aubé, J. Pri
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pyridoxal phosphate dependent enzym
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Vinylglycines are also useful as sy
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In 1984, a modified Strecker synthe
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The main byproduct of elimination w
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, HO- OH Scheme 3.14 , 1) pb(OAc),
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L-vinylglycine has also been synthe
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Ser(a1d)-OB0 gave the desired olefi
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A tram relationship for H2IH3 in th
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33 Summary The Cbz OB0 ester protec
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67.1 (Ar_cH20), 63.2 @--a), 56.3 (a
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yielded a slightiy yellowish solid
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JAS Grigiarà ddition of trimethyls
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6 158.9 (CONH), 107.4 (OB0 ester C-
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Rutjes, F.P.J.T.; Wolf, L.B.; Schoe
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(a) Tashiro, T.; Fushiya, S.; Nome,
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Sawada, S.; Nakayama, T.; Esaki, N.
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of Rheum rhaponticum over forty yea
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Glutamic acid derivatives are aiso
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syntheses exist for the functionaii
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4.1.4 Synthesis of Optically Active
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4.1.4.3 Catalytic HydrogeMrion The
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Scheme 4.10 C02Et CO*Et R=Me, Et, P
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stereochemicaî induction at the re
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protected glutamate did not adopt a
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Scheme 4.16 The first synthesis of
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stereoselectivi ty during electroph
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kt, when we repeated the synthesis
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CbzH Scheme 4.2û OH pTsW CbzH Figu
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5.21 5.00 16.63 Figure 4.5: GCMS of
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Glu(y-Me)(OMe)OBO ester 4.73. Howev
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OB0 ester. Moreover, the stereochem
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Table 4.1: Optimilgtion of Methyiat
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Scheme 4.22 M'2aL O 2) 1) LiHMDS, P
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Table 4.2: Optimization of Hydroxyi
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Cb2H 1 OsO,. NMO acetone:H& OH m 2)
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The direct electrophilic azidizatio
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to the mesylate Alûû in 80% yield
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which were not isolated. ESI-MS and
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concentrateci reaction mixhue of 4.
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and during acid hydrolysis. HPLC an
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A general method for the synthesis
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Generai Procedure for Removd of Rot
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Same procedure as in 4.4.1. TU3 (1:
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Same procedure as in 4.4.3. [al% =
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ffom CH2Cl2) 3338,2962,2875, 1732,
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ester -0). 72.4 (OB0 ester w20), 65
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4m4.11 5-Methyl-(~,~-2-[(betl~gIo~)
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= l2JHz, CbzCHHO), 3.87-3.78 (s + r
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1016; HRMS (FAB) calcd for (M + H+)
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7.3&, CHZCH~), 0.78 (s, 3H, OB0 est
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hotu before benzyl brornide (0.21 m
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1 H. J = 10.3Hz (detennined by deco
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378.22; Anal. cdcd for CI9Ha07: C,
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(ça), 164.0 EONH), 143.3 (Cbz==).
Page 233 and 234:
min. The solvent was removed under
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173.8 c=O), 156.3 CONH), 137.6 ( Cb
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mp. 1 16- 1 165°C; [al2'D = -2 1 .
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(3:2 Et0Ac:hexanes) to give 4.99 (1
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Cbz-L-Glu(Z-B,y-dehydro)(OMe)OBO 49
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(CbzQI20), 57.4 (am, 39.8 (yCJS2),
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3.7, 10.7, 14.5Hz. BCHH), 0.76 (S.
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TLC (1:1, EtOAc:Hex), Rc = 0.35; 'H
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1515, 1227, 1048, 1016,909; ESI-MS
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(Cbz=@), 128.5, 128.2, 128.1 (a-=),
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TU3 ( 1 : 1, EtOAc:Hex), Rf = 0.17;
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4-4-46 (2S,4S)-2-My14aminopentanedi
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give 0.020 g (54%) of the monoamrno
Page 259 and 260:
1. (a) Virtanen, A.I.; Berg, A.M. A
Page 261 and 262:
Bory, S.; Dubois, J.; Gaudry, M.; M
Page 263 and 264:
(a) Ezquerra, J.; Pedregal, C.; Ymr
Page 265 and 266:
(a) Blaskovich, M.A.; Lajoie. G.A.
Page 267 and 268:
Rathke, M-W.; Sullivan, D.F. J. Am,
Page 269 and 270:
Chapter Five Stereoselective Synthe
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of p-methylaspartate 5.1 to glutama
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OAc Ac kfN&O@ 5.8 C02Et AC lU&02Et
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of 2:7 respectively, both of which
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MH). Changing the reaction conditio
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Garner's aldehyde 1.53 was also use
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Rotected ~-aminoaspartate Sm6 was s
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amount of unreacted starting materi
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provided crystals of sufficient qua
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5.2.2 Addition of Other AIkylation
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Scheme 5-18 We also investigated az
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5.2.5 Discussion of the Stereochist
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face) to give rise to the B,3S ster
Page 295 and 296:
The synthesis of threo-L-b-substitu
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TU3 (1: 1, CHC13:EtOAc, 1 % AcOH) R
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156.0 (ÇONH), 1 36.2 (Cbz*), 128.5
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ester COI3), 30.6 (p-cH2), 14.1 (OB
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extracted with EtzO (3 x 25 d), the
Page 305 and 306:
TU3 (1: 1, EtOAc:Hex), Rr = 0.48; '
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63 MHz) 6 175.9 cd), 156.0 EONH), 1
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175.1 CC-O), 155.8 (CONH), 136.1 (C
Page 311 and 312:
'H-NMR @20, 300 MHz) 6 7.26-7.03 (m
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12.7Hz, CbzCHHO), 5.02 (ci, lH, J =
Page 315 and 316:
TU3 ( 1 : 1, EtOAc:Hex), Rr = 0.40;
Page 317 and 318:
1. 2. 3. 4. 5. 6. 7. 8. 9. IO. 11.
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Eager, R.G. Jr.; Baltimore, B.G.; H
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- - Sardina, F.J.; Paz, MM.; Femihd
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Chapter Si Solid Phase Synthesis of
Page 325 and 326:
eactions such as the Ugi condensati
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Dehydroamino acids have also been u
Page 329 and 330:
Pyroglutarnate was reduced into the
Page 331 and 332:
. - 6.2.1 Synthesis of Resin-Bod BH
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" 6.29 NMM, CH& Scheme 6.11 The arn
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esin placed hem Figure 6.3: Experim
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Figure 6.4: MAS 13c-N..~ (500 MHz)
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Table 6.1: Addition of R'M~B~ to 6.
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63 Summ Attachrnent of Ser-OB0 este
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(S. 2H, CbzCHzO), 4.57-4.40 (m, 7H,
Page 345 and 346:
I C-O), 7 1.9 (OB0 ester GHzO), 61.
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insed, altemating with dry DMF (5 x
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- MAS 'H NMR (Spin-Echd ms): 8 3.87
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6.4.16 (zs)-2-Pmmo-3-hydroruy-3-met
Page 353 and 354:
O.; Gilliarn, CL.; Boisclair, M.D.;
Page 355 and 356:
38. Rakita, P.E.; Silverman, G.S. W
Page 357 and 358:
of these important derivatives due
Page 359 and 360:
the glutamate dimer. It may also be
Page 361 and 362:
Rose, N.G.W.; Blaskovich, M.A.; Won
Page 363 and 364:
Appendices
Page 365 and 366:
Table 1, Cryatrl data and .tructuse
Page 367 and 368:
Tabla 3. Bond langths [Al and amglr
Page 369 and 370:
- - - . - Table 5. Eyârogen coordi
Page 371 and 372:
Calculation of Free Energy Dinerenc
Page 373 and 374:
Table 1. Crymtal data and mtructure
Page 375 and 376:
. Tabla 3. Bond lenpths [il and rng
Page 378 and 379:
X-Ray Crystallographic Data for Com
Page 380 and 381:
4 Tabla 2. Atomic coordinates 1 x 1
Page 382 and 383:
2 3 ? able 4. Aniiotsopic dfmplacea
Page 384 and 385:
Calcdation to Determine Resin Loadi
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Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

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