✦ LIBER ✦
Asymmetric Synthesis via Heterocyclic intermediates, L. – Trichloroacetimidates, II. Asymmetric Synthesis of α-Amino Acid Benzyl Esters via the Bisbenzyl Bislactim Ether of cyclo(-L-Val-Gly-)
✍ Scribed by Groth, Ulrich ;Schmeck, Carsten ;Schöllkopf, Ulrich
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 322 KB
- Volume
- 1993
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
The diketopiperazine cyclo(‐L‐Val‐Gly‐) (1) can be O‐alkylated under mild acidic reaction conditions with the alkyl trichloroacetimidates 2 to the corresponding bisalkyl bislactim ethers. Alkylation of the bisbenzyl bislactim ether anion of cyclo(‐L‐Val‐Gly‐) 4c with benzyl bromide and subsequent hydrolysis with aqueous trifluoroacetic acid afforded D‐phenylalanine benzyl ester (8) with an enantiomeric excess of > 95%.