Nb-Methoxycarbonyltryptophan methyl ester (dl- and l-13) was cyclized to the corresponding rans cyclic tautomer (14) in excellent yield in various acids such as 85% phosphoric acid or trifluoroacetic acid. The cis cyclic tautomer (15) was formed as the less stable and kinetically controlled product and converted to the more stable trans isomer (14) under the reaction condition. The trans isomer (14)
Ñ b -Methoxycarbonyltryptophan甲酯(DL-和1- 13)环化为相应的RANs环状互变异构体(14,在各种酸如85%的
磷酸或
三氟乙酸优良产率)。的顺式环互变异构体(15)形成为较不稳定的和动力学控制的产品,并转换为更稳定的反式异构体(14反应条件下)。用10%
硫酸的
甲醇溶液处理,将反式异构体(14)还原为13。其他色
氨酸和
色胺衍
生物(6和19a)在相似的酸性介质中也被环化成相应的环状互变异构体。