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[摘要]:The non-proteinogenic amino acids contained in callipeltins, (3S, 4R)-3, 4-dimethyl-L-pyroglutamic acid and D-allothreonine, were synthesized from D- or L-serine. The stereoselective synthesis of two methyl groups of (3S, 4R)-3, 4-dimethyl-L-pyroglutamic acid was accomplished by diastereoselective hydrogenation and alkylation. Kinetic epimerization of the C-4 methyl substituent followed by Boc-deprotection with 10% TFA gave the desired (3S, 4R)-3, 4-dimethyl-L-pyroglutamic acid as a single isomer. |
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