Synthesis of the phthalide isoquinoline alkaloids (-)-egenine, (-)-corytensine, and (-)-bicuculline by asymmetric carbonyl addition of chiral dipole-stabilized organometallics
摘要:
The asymmetric addition of metalated [(methylenedioxy)isoquinolyl]oxazolines is 100% selective for the erythro (alpha-hydroxybenzyl)isoquinoline diastereomers, with 2:1 selectivity of the two possible erythro stereoisomers. Enrichment to 100% ee after removal of the auxiliary and conversion to (-)-bicuculline and (+)-bicuculline diol establish the absolute configuration of the major addition product. Inversion of the C-9 hydroxyl affords entry into the threo series as well. The asymmetric carbonyl addition was used to synthesize, for the first time, the phthalide-isoquinoline hemiacetals corytensine and egenine, confirming the previously assigned structures and absolute configurations, and establishing the identity of egenine with decumbensine and of corytensine with epi-alpha-decumbensine.
Short synthesis of noscapine, bicuculline, egenine, capnoidine, and corytensine alkaloids through the addition of 1-siloxy-isobenzofurans to imines
作者:Maria Del Pilar C. Soriano、Nagula Shankaraiah、Leonardo Silva Santos
DOI:10.1016/j.tetlet.2010.01.104
日期:2010.3
A concise diastereotioselective strategy for the synthesis of noscapine, bicuculiine, and egenine (1a-c), as well as capnoidine and corytensine (2a,b), was developed using diastereoselective addition of 1-siloxy-isobenzofurans 4a and 4b to immium ion 5 in a one-pot approach. The synthesis features the use of imine 13 obtained through Bischler-Napieralsky reaction from airline 11. The addition of ionic liquids as addictives in the reactions afforded erythro configuration in major adduct compounds. The synthetic route can also be applied in the total synthesis of promising tubulin binding agent EM105 (3). (C) 2010 Elseviet Ltd. All rights reserved.
REIN, KATHLEEN S.;GAWLEY, ROBERT E., TETRAHEDRON LETT., 31,(1990) N6, C. 3711-3714
作者:REIN, KATHLEEN S.、GAWLEY, ROBERT E.
DOI:——
日期:——
REIN, KATHLEEN S.;GAWLEY, ROBERT E., J. ORG. CHEM., 56,(1991) N, C. 1564-1569