SYNTHESIS OF RACEMIC ALPHA-AMINO CARBOXAMIDES VIA LEWIS ACID-MEDIATED REACTIONS OF ALPHA-METHOXYGLYCINAMIDE DERIVATIVES WITH ALLYLSILANES - ENZYMATIC RESOLUTION TO OPTICALLY-ACTIVE ALPHA-AMINO-ACIDS

A short and expedient synthetic route to optically active, saturated and gamma,delta-unsaturated alpha-amino acids is reported. The key step is a BF3.OEt2-mediated reaction of allylsilanes with N-(alkoxycarbonyl)-alpha-methoxyglycinamides 11-15, leading to the corresponding gamma,delta-unsaturated a...

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Bibliographic Details
Published inJournal of organic chemistry Vol. 57; no. 25; pp. 6769 - 6778
Main Authors ROOS, EC, MOOIWEER, HH, HIEMSTRA, H, SPECKAMP, WN, KAPTEIN, B, BOESTEN, WHJ, KAMPHUIS, J
Format Journal Article
LanguageEnglish
Published WASHINGTON Amer Chemical Soc 04.12.1992
American Chemical Society
Subjects
Aliphatic compounds
Chemistry
Chemistry, Organic
Exact sciences and technology
Organic chemistry
Physical Sciences
Preparations and properties
Science & Technology
CATALYSIS
ALLYL
ALKYLATION
SILICON
ESTERS
CATION EQUIVALENTS
PROTECTION-DEPROTECTION
AMIDES
Lewis acid
α-Aminoacid
Aliphatic compound
Optical resolution
Silicon Organic compounds
Hydroxamic acid
Chiral compound
Acid catalysis
Ethylenic compound
Enzymatic reaction
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Summary:A short and expedient synthetic route to optically active, saturated and gamma,delta-unsaturated alpha-amino acids is reported. The key step is a BF3.OEt2-mediated reaction of allylsilanes with N-(alkoxycarbonyl)-alpha-methoxyglycinamides 11-15, leading to the corresponding gamma,delta-unsaturated alpha-aminocarboxamides. The genuine S(N)1-character of this process with iminium ion 6 as intermediate is proven in the case of the glycine ester 10. Thus, reaction of enzymatically resolved 10 with pi-nucleophiles leads to racemic products. The most useful iminium precursors are the N-methoxyamides 12-14 providing good yields of coupling products. The most convenient N-protective group is the allyloxycarbonyl group. Deprotection proceeds via a Pd(0)-catalyzed transprotection to the corresponding BOC-protected analogues. Four examples of the enzymatic resolution of alpha-amino carboxamides, by using an L-specific aminopeptidase from Pseudomonas putida, are described in detail. Most notably, secondary N-methoxyamides are good substrates for the enzyme to provide the desired a-amino acids in high optical purity.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo00051a019