Cyclic tautomers of tryptophans and tryptamines. VIII. Cyclic tautomers of cyclo-L-prolyl-L-tryptophyl and related compounds.
作者:MIKIO TANIGUCHI、ICHIRO YAMAMOTO、MASAKO NAKAGAWA、TOHRU HINO
DOI:10.1248/cpb.33.4783
日期:——
Two diastereomers (6 and 7) of the cyclic tautomer of cyclo-L-propyl-L-tryptophyl (5) have been prepared by dissolving 5 in 85% phosphoric acid or trifluoroacetic acid. The stable isomer (6) was obtained in 89% yield on the acid treatment of 5 at room temperature. Cyclic tautomers (15 and 17) of the related 2, 5-piperazinediones (14 and 16) have also been prepared. Hydroxylation of the N-acetyl cyclic tautomers (8 and 9) with lead tetraacetate in trifluoroacetic acid followed by methylation gave the 8- and 9-methoxy derivatives (18, 19, 21, and 22) in moderate yields. The 9-methoxy derivative (22) was the major product of the oxidation of 9. On the other hand, oxidation of 5 in trifluoroacetic acid with lead tetraacetate followed by reduction with zinc gave the 8-hydroxy derivative (28) selectively in good yield via the cyclic tautomer (26) and the quinoneimine (27).
通过将 5 溶解在 85% 的磷酸或三氟乙酸中,制备出了环-L-丙基-L-色氨酰(5)环状同分异构体的两种非对映异构体(6 和 7)。在室温下对 5 进行酸处理后,得到了稳定的异构体(6),收率为 89%。相关的 2,5-哌嗪二酮(14 和 16)的环状同分异构体(15 和 17)也已制备出来。用四乙酸铅在三氟乙酸中对 N-乙酰基环状同系物(8 和 9)进行羟基化反应,然后进行甲基化反应,得到了 8-和 9-甲氧基衍生物(18、19、21 和 22),收率中等。另一方面,用四乙酸铅在三氟乙酸中氧化 5,然后用锌还原,通过环状同分异构体 (26) 和醌亚胺 (27),选择性地得到 8-羟基衍生物 (28),收率很高。