Synthesis of methionine carrying a chiral methyl group and its use in determining the steric course of the enzymatic C-methylation of indolepyruvate during indolmycin biosynthesis.
Synthesis of methionine carrying a chiral methyl group and its use in determining the steric course of the enzymatic C-methylation of indolepyruvate during indolmycin biosynthesis.
复制标题
携带手性甲基的甲硫氨酸的合成及其在测定吲哚霉素生物合成过程中吲哚丙酮酸酶促 C-甲基化的空间过程中的用途。
DOI：
10.1021/ja00443a062
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发表时间：
1977
影响因子：
15
通讯作者：
H. Floss
中科院分区：
文献类型：
--
作者：
L. Mascaro;R. Horhammer;S. Eisenstein;L. Seller;K. Mascaro;H. Floss
Eggerer’s procedure. 4 In this procedure the acetate sample is enzymatically convertedto malate which is then equilibrated with fumarase. During equilibration, malate samples synthe-sized from the S-isomer of acetate retain less than half of their tritium while samples synthesized from the/?-isomer retain more than half of their tritium. The first step in the synthesis of methionine is the Schmidt degradation of acetate to methylamine, 6 which is trapped as the hydrochloride and tosylated by heatingwith/i-toluenesulfonyl chloride in 10% aqueous NaOH. The second tosyl group is introduced by refluxing the monotosylate, p-tolu-enesulfonyl chloride, and K2CO3 in anhydrous xylene. The key step in the sequence is the use of the ditosylimide function as a leaving group in the alkylation of the homocysteine anion with the chiral methyl group. 7· 8 This reaction was performed, under an argon atmosphere, by treating a suspension of ben-zyl-L-homocysteine in HMPA with Na-K alloy, followed by addition of the ditosylimide and heating to 80 C. Methionine was purified by ion exchange (Dowex 50W, 10% NH4OH) and thin layer (silica gel 60 F-254, 1-butanol-acetic acid-^ O 4: 1: 1) chromatography. The Schmidt reaction is known9 to proceed with retention of configuration and the ditosylimide displacement should involve inversion of configuration, race-mization being the only plausible alternative. 10 Thus, S-[2-
