The 5-bromo derivative 2 of the cyclic tautomer of N(b)-methoxycarbonyl-L-tryptophan methyl ester 1 undergoes reaction with CuCN in refluxing N-methylpyrrolidone (NMP) to give 5-cyano derivative 3a with some ring opened 5-cyano product 3b. Both 3a and 3b can be converted, in high yield, into free 5-cyano-L-tryptophan 4 with BBr3 under mild conditions.
The 5-bromo derivative 2 of the cyclic tautomer of N(b)-methoxycarbonyl-L-tryptophan methyl ester 1 undergoes reaction with CuCN in refluxing N-methylpyrrolidone (NMP) to give 5-cyano derivative 3a with some ring opened 5-cyano product 3b. Both 3a and 3b can be converted, in high yield, into free 5-cyano-L-tryptophan 4 with BBr3 under mild conditions.
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。
Total Synthesis of (+)-Elacomine and (?)-Isoelacomine, Two Hitherto Unnamed Oxindole Alkaloids fromElaeagnus commutata
Racemic elacomine ((±)-2), a hemiterpene spiro oxindole alkaloid from Elaeagnus commutata, was synthesized in five steps from 6-methoxytryptamine (19) in 16% overall yield (Scheme 3). The final oxidative rearrangement of the corresponding β-carboline precursor (±)-21 furnished isoelacomine ((±)-22) as a by-product (6% overall yield). A more elaborate route that started from L-tryptophan furnished (+)-2
Synthesis of 5-Alkyl- and 5-Aryl-L-Tryptophan Analogues via Palladium-Catalyzed Cross-Coupling of an Iodinated Cyclic Tryptophan Tautomer
作者:David E. Zembower、Matthew M. Ames
DOI:10.1055/s-1994-25708
日期:——
Cyclic tryptophan tautomers have been shown to be useful intermediates in the preparation of optically pure tryptophans substituted in the benzenoid ring. We have utilized cyclic tautomer 2a for the preparation of L-tryptophan derivatives bearing 5-alkyl and 5-aryl functionalities. Treatment of 2a with 4 equivalents of iodine monochloride provided the 5-iodo species 3a in 81% yield. Cross-coupling of 3a with arylboronic acids or B-alkyl-9-borabicyclo[3.3.1]nonane derivatives, catalyzed by 3 mol% [bis(1,1′-diphenylphosphino)ferrocene]palladium(II) chloride, afforded the 5-aryl and 5-alkyl cyclic tryptophan tautomers 3b-g in 59-79% yields. The cyclic tautomers were easily decyclized and deprotected to give the corresponding 5-aryl- and 5-alkyl-L-tryptophans.