Bischler–Napieralski cyclization of the known phenylacetamide 1, followed by selective ether cleavage of the 3,4-dihydroisoquinoline 2 and sodium borohydride reduction, afforded the tetrahydroisoquinoline 4. Optical resolution of 4 with tartaric acid gave the optical isomers 4a,b, which were converted into the 6-ketomorphinans 9a,b and their O-methyl ethers 10a,b by the following reaction sequence: Birch reduction, N-formylation of the dihydro bases, Grewe cyclization, removal of the N-formyl protecting groups, reductive N-methylation, and O-methylation. The 2-deoxy congeners 12a,b were obtained from 9a,b by phenyltetrazolylation, and catalytic removal of the heterocyclic etherfunction. The (−)-enantiomer 12a obtained by this synthesis was identical with material prepared from natural morphine, and exhibited the high antinociceptive potency already reported.
已知苯乙酰胺1经Bischler–Napieralski环化反应后,经过选择性醚解离生成3,4-二氢异喹啉2,再经过硼氢化钠还原,得到四氢异喹啉4。用酒石酸对4进行光学分离得到光学异构体4a,b,随后经过以下反应序列将其转化为6-酮吗啡烷9a,b及其O-甲基醚10a,b:桦木还原、二氢碱的N-甲酰化、Grewe环化、去除N-甲酰保护基、还原N-甲基化和O-甲基化。通过苯基四氮唑化反应和催化去除杂环醚功能,将9a,b转化为2-脱氧同分异构体12a,b。通过该合成方法得到的(−)-对映体12a与从天然吗啡制备的物质相同,并且展现出已报道的高抗痛性能。