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Titolo:
Asymmetric synthesis of alpha-substituted serines
Autore:
Sano, S; Nagao, Y;
Indirizzi:
Univ Tokushima, Fac Pharmaceut Sci, Tokushima 7708505, Japan Univ Tokushima Tokushima Japan 7708505 eut Sci, Tokushima 7708505, Japan
Titolo Testata:
JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN
fascicolo: 8, volume: 58, anno: 2000,
pagine: 756 - 765
SICI:
0037-9980(200008)58:8<756:ASOAS>2.0.ZU;2-#
Fonte:
ISI
Lingua:
JPN
Soggetto:
ALDOL-TYPE REACTION; ISARIA-SINCLAIRII METABOLITE; PIG-LIVER ESTERASE; SILYL ENOL ETHERS; AMINO-ACIDS; ENANTIOSELECTIVE SYNTHESIS; DIASTEREOSELECTIVE ALKYLATION; ENANTIODIVERGENT PROCEDURE; STEREOSELECTIVE SYNTHESIS; MYRIOCIN THERMOZYMOCIDIN;
Keywords:
alpha-substituted serine; amino acid; asymmetric synthesis; bislactim ether; alkylation; aldol reaction; enzyme reaction; (-)-sparteine; ISP-I; (+)-conagenin;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
74
Recensione:
Indirizzi per estratti:
Indirizzo: Nagao, Y Univ Tokushima, Fac Pharmaceut Sci, 1-78 Sho Machi, Tokushima 7708505, Japan Univ Tokushima 1-78 Sho Machi Tokushima Japan 7708505 505, Japan
Citazione:
S. Sano e Y. Nagao, "Asymmetric synthesis of alpha-substituted serines", J SYN ORG J, 58(8), 2000, pp. 756-765

Abstract

Novel methodologies for the preparation of alpha-substituted serines are described. A newly designed bislactim ether, ethyl(55)- or (5R)-3, 6-diethoxy-2,5-dihydro-5-isopropyl-2-pyrazinecarboxylate, was treated with base or Lewis acid-tertiary amine to generate an enolate or enaminate (imine anion, metalloenamine). Alkylation or aldol-type reaction with the resultant enolate or enaminate proceeded in a highly diastereoselective manner to give thecorresponding products. Reduction of these diastereomers followed by hydrolysis afforded the desirable alpha-substituted serines. The highly enantioselective aldol-type reaction of an achiral bislactim ether, ethyl 3,6-diethoxy-2,5-dihydro-2-pyrazinecarboxylate, was also achieved by employing Sn(OSO2CF3)(2)-triethylamine in the presence of a catalytic amount of (-)-sparteine. Interestingly, the stereoselective outcome of the Sn(II)-mediated reaction differed from that of the Mg(II)-mediated one in the aldol-type reaction of the bislactim ethers with aliphatic aldehydes. On the other hand, chemoenzymatic synthesis of enantiomerically pure alpha-substituted serines must also be a convenient and useful procedure. Porcine liver esterase (PLE) or rabbit; liver esterase (RLE) catalyzed hydrolysisof the pro-S ester group of diethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates to afford (R)-ethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates each in excellent enantiomeric excess. Enantiodivergent reductions of these acid esters readily furnished both the corresponding enantiomeric alpha-substituted serines. Finally, the application of these methodologies mentioned above to a totalsynthesis of ISP-I (a potent immunosuppressant) and (+)-conagenin (a low molecular weight immunomodulator) is described.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 22/01/20 alle ore 22:14:24