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

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Figure 5.4: A) Chdation controlled mode1 of (E)-lithium enolate of 5.38. B) Nonchelation del dth (2)-lithium enolate of 538. Unexpectedly, the 13-addition to glutamates described in chapter four occurs in higher selectivity than in the case of 12-addition to aspartate derivatives. Of significance, the extra methylene unit in glutamate 4.69 allows rotation of the (2)-enolate described in figure 4.10 into a position in which it may chelate with the N-Li bond. As such, both the (E)- and (%nolate may adopt the same transition state to give high selectivity in which the geometry of the enolate is imlevant.
The synthesis of threo-L-b-substituted aspartic acids has been described, with selectivities ranging frorn as high as 10:l to 1:l and in overall yields of 5-281 in six steps. The aspartate 5 3 was synthesized in good overall yield and its crystalline nature made its use as a synthon particularly convenient The stereoselectivity of methylation of Cbz-Asp(0Me)OBO 5.38 occurred in a 10: 1 ratio and is comparable to the best reported proceduren' for the synthesis of 2S,3S-methylaspartate, but is preferable in terms of atom efficiency. Inverse addition of the substrate to base at -78°C is necessary for high selectivity. Disappointingly a rapid decrease in stereoselectivity occurs with bulkier reagents, from 4: 1 with aiiyl bromide to 1: 1 selectivity with trisyl azide, the reasons for which are still unclear. Deprotection in refluxing 6N HCl and cation exchange gave the $-substituted aspartic acids in 32-68% yield.
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Solution and Solid Phase Synthesis
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The University of Waterloo requires
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Many people have made the experienc
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Table of Contents Abstract ........
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23 Summary ........................
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5.1.4.1 Enzymatic Methods .........
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List of Tables Table 2.1 Table 2.2
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Figure 4.1 O Figure 5.1 Figure 5.2
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CYS d DAST DBAD DBU DCC de DEAD dec
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NMP Nu OB0 ester PEG Ph Phe PhFl Ph
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1.1 General Introduction Chapter On
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acids will be presented including a
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.J generation of the enolate and ad
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classical techniques (Scheme 1.7) a
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s~ccess.~ The same principle has be
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O Scheme 1.11 O R1,qH2 m OH RI= H,
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stereosele~tivities.~ Numerous exam
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Williams and coworlcers have examin
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template, reaction with alkyl halid
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The 3-bromo analog of Williams and
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formation of serine aldehydes; dire
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Scheme 1.24 R dimethoxy- R ProPane
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of thiol trityl led to racemic cyst
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nucleophiles such as acetate and im
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may be employed, while the oxidatio
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Several methods for the removal of
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1.5 References Barrett, G.C. Chemis
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(a) Schmidt, U.; Meyer, R.; Leitenb
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R.M. Tetrahedron Le#. 2001,42, 769.
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(a) Lubell, W.D.; Rapport, H. J. Am
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Nakajima, K.; Takai, F.; Tanaka, T.
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2.1 Introduction Chapter Two Synthe
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2.1.1 Synthesis of SHydroxy-a-Amino
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typically generated in both poor yi
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2.1.3.3 Electrophilic%Nucfeophilic
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Scheme 2.8 2-(Arylthi0)-2-nitrooxir
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Scheme 2.10 Schollkopf et al. have
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2.1.3.5 Synthesis fiom #-Amino Acid
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HO Scheme 2.17 This laboratory prev
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Scheme 2.19 NaBr, acetone The best
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equires carefiil attention to preve
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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
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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
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(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==).
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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
Page 243 and 244: (CbzQI20), 57.4 (am, 39.8 (yCJS2),
Page 245 and 246: 3.7, 10.7, 14.5Hz. BCHH), 0.76 (S.
Page 247 and 248: TLC (1:1, EtOAc:Hex), Rc = 0.35; 'H
Page 249 and 250: 1515, 1227, 1048, 1016,909; ESI-MS
Page 251 and 252: (Cbz=@), 128.5, 128.2, 128.1 (a-=),
Page 253 and 254: TU3 ( 1 : 1, EtOAc:Hex), Rf = 0.17;
Page 255 and 256: 4-4-46 (2S,4S)-2-My14aminopentanedi
Page 257 and 258: 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
Page 271 and 272: of p-methylaspartate 5.1 to glutama
Page 273 and 274: OAc Ac kfN&O@ 5.8 C02Et AC lU&02Et
Page 275 and 276: of 2:7 respectively, both of which
Page 277 and 278: MH). Changing the reaction conditio
Page 279 and 280: Garner's aldehyde 1.53 was also use
Page 281 and 282: Rotected ~-aminoaspartate Sm6 was s
Page 283 and 284: amount of unreacted starting materi
Page 285 and 286: provided crystals of sufficient qua
Page 287 and 288: 5.2.2 Addition of Other AIkylation
Page 289 and 290: Scheme 5-18 We also investigated az
Page 291 and 292: 5.2.5 Discussion of the Stereochist
Page 293: face) to give rise to the B,3S ster
Page 297 and 298: TU3 (1: 1, CHC13:EtOAc, 1 % AcOH) R
Page 299 and 300: 156.0 (ÇONH), 1 36.2 (Cbz*), 128.5
Page 301 and 302: ester COI3), 30.6 (p-cH2), 14.1 (OB
Page 303 and 304: extracted with EtzO (3 x 25 d), the
Page 305 and 306: TU3 (1: 1, EtOAc:Hex), Rr = 0.48; '
Page 307 and 308: 63 MHz) 6 175.9 cd), 156.0 EONH), 1
Page 309 and 310: 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
Page 313 and 314: 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.
Page 319 and 320: Eager, R.G. Jr.; Baltimore, B.G.; H
Page 321 and 322: - - Sardina, F.J.; Paz, MM.; Femihd
Page 323 and 324: Chapter Si Solid Phase Synthesis of
Page 325 and 326: eactions such as the Ugi condensati
Page 327 and 328: 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
Page 333 and 334: " 6.29 NMM, CH& Scheme 6.11 The arn
Page 335 and 336: esin placed hem Figure 6.3: Experim
Page 337 and 338: Figure 6.4: MAS 13c-N..~ (500 MHz)
Page 339 and 340: Table 6.1: Addition of R'M~B~ to 6.
Page 341 and 342: 63 Summ Attachrnent of Ser-OB0 este
Page 343 and 344: (S. 2H, CbzCHzO), 4.57-4.40 (m, 7H,
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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
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O.; Gilliarn, CL.; Boisclair, M.D.;
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38. Rakita, P.E.; Silverman, G.S. W
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of these important derivatives due
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the glutamate dimer. It may also be
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Rose, N.G.W.; Blaskovich, M.A.; Won
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Appendices
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Table 1, Cryatrl data and .tructuse
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Tabla 3. Bond langths [Al and amglr
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- - - . - Table 5. Eyârogen coordi
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Calculation of Free Energy Dinerenc
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Table 1. Crymtal data and mtructure
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. Tabla 3. Bond lenpths [il and rng
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X-Ray Crystallographic Data for Com
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4 Tabla 2. Atomic coordinates 1 x 1
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2 3 ? able 4. Aniiotsopic dfmplacea
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Calcdation to Determine Resin Loadi
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Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

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