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Asymmetric synthesis of 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI).


ABSTRACT: A short, asymmetric synthesis of the 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) analogue of the CC-1065 and duocarmycin DNA alkylation subunits is described. Treatment of iodo-epoxide 5, prepared by late-stage alkylation of 4 with (S)-glycidal-3-nosylate, with EtMgBr at room temperature directly provides the optically pure alcohol 6 in 87% yield (99% ee) derived from selective metal-halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. The use of MeMgBr or i-PrMgBr also provides the product in high yields (82-87%), but requires larger amounts of the Grignard reagent to effect metal-halogen exchange and cyclization. Direct transannular spirocyclization of 7 following O-debenzylation of 6 provides N-Boc-CBI. This approach represents the most efficient (9-steps, 31% overall) and effective (99% ee) route to the optically pure CBI alkylation subunit yet described.

SUBMITTER: Lajiness JP 

PROVIDER: S-EPMC3079324 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Asymmetric synthesis of 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI).

Lajiness James P JP   Boger Dale L DL  

The Journal of organic chemistry 20101230 2


A short, asymmetric synthesis of the 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) analogue of the CC-1065 and duocarmycin DNA alkylation subunits is described. Treatment of iodo-epoxide 5, prepared by late-stage alkylation of 4 with (S)-glycidal-3-nosylate, with EtMgBr at room temperature directly provides the optically pure alcohol 6 in 87% yield (99% ee) derived from selective metal-halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. The use of Me  ...[more]

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