Enantiocontrolled synthesis of burseran, brassilignan, dehydroxycubebin, and other tetrahydrofuran lignans in both enantiomeric forms. Application of intermolecular nitrile oxide cycloadditions and lipase-mediated kinetic resolutions
摘要:
Several natural and unnatural tetrahydrofuran lignans have been synthesized by a convergent approach. Our methodology utilizes a nitrile oxide cycloaddition to dihydrofuran 8 and an enzymatic resolution of alcohols 11 by lipase PS. The lipase-mediated kinetic resolution of alcohols 11 furnished both enantiomers of the lignan precursors 12 and 14 in high optical purity (>99% ee). This is followed by a S(N)2 displacement of tosylates 15 and 18 by alpha-lithiobenzyl phenyl sulfides. In this manner, both enantiomers of 3,4-dibenzyltetrahydrofuran (17a, 20a), 3,4-bis(3-methoxybenzyl)-tetrahydrofuran (17b, 20b), brassilignan (17c, 20c), dehydroxycubebin (17d, 20d), and burseran (17e, 20e) were synthesized in overall yields of 6-16%.
Enantiocontrolled synthesis of burseran, brassilignan, dehydroxycubebin, and other tetrahydrofuran lignans in both enantiomeric forms. Application of intermolecular nitrile oxide cycloadditions and lipase-mediated kinetic resolutions
摘要:
Several natural and unnatural tetrahydrofuran lignans have been synthesized by a convergent approach. Our methodology utilizes a nitrile oxide cycloaddition to dihydrofuran 8 and an enzymatic resolution of alcohols 11 by lipase PS. The lipase-mediated kinetic resolution of alcohols 11 furnished both enantiomers of the lignan precursors 12 and 14 in high optical purity (>99% ee). This is followed by a S(N)2 displacement of tosylates 15 and 18 by alpha-lithiobenzyl phenyl sulfides. In this manner, both enantiomers of 3,4-dibenzyltetrahydrofuran (17a, 20a), 3,4-bis(3-methoxybenzyl)-tetrahydrofuran (17b, 20b), brassilignan (17c, 20c), dehydroxycubebin (17d, 20d), and burseran (17e, 20e) were synthesized in overall yields of 6-16%.
Enantiocontrolled synthesis of burseran, brassilignan, dehydroxycubebin, and other tetrahydrofuran lignans in both enantiomeric forms. Application of intermolecular nitrile oxide cycloadditions and lipase-mediated kinetic resolutions
作者:Janet A. Gaboury、Mukund P. Sibi
DOI:10.1021/jo00060a037
日期:1993.4
Several natural and unnatural tetrahydrofuran lignans have been synthesized by a convergent approach. Our methodology utilizes a nitrile oxide cycloaddition to dihydrofuran 8 and an enzymatic resolution of alcohols 11 by lipase PS. The lipase-mediated kinetic resolution of alcohols 11 furnished both enantiomers of the lignan precursors 12 and 14 in high optical purity (>99% ee). This is followed by a S(N)2 displacement of tosylates 15 and 18 by alpha-lithiobenzyl phenyl sulfides. In this manner, both enantiomers of 3,4-dibenzyltetrahydrofuran (17a, 20a), 3,4-bis(3-methoxybenzyl)-tetrahydrofuran (17b, 20b), brassilignan (17c, 20c), dehydroxycubebin (17d, 20d), and burseran (17e, 20e) were synthesized in overall yields of 6-16%.