|Budget Amount *help
¥5,800,000 (Direct Cost : ¥5,800,000)
Fiscal Year 1994 : ¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1993 : ¥3,800,000 (Direct Cost : ¥3,800,000)
The purpose of this work is to develop the new method for asymmetric synthesis using enantiomerically defined alpha-oxystannanes. A summary of the research results is as follow :
(1) A new practical method for asymmetric synthesis of alpha-hydroxystannanes
The TiCl_4-promoted reaction of (4S,6S) - (4,6-dimethyl-1,3-dioxan-2-yl) tributylstannane with Grignard reagents is shown to sfford, after oxidation followed by base treatment, the (S) -alpha-hydroxystannanes in >95-20% ee.
(2) Asymmetric [2,3] -Wittig rearrangement
The [2,3] -Wittig rearrangement of enantiomerically-defined alpha- (allyloxy) stannanes, prepared from (S) -1-tributylstannyl-1-propanol, with butyllithium is shown to proceed with essentially complete inversion of configuration at the Li-bearing migrating terminus.
(3) Asymmetric [1,2] -Wittig rearrangement
The [1,2] -Wittig rearrangements of enantio-defined alpha-benzyloxypropyllithium and its (R) -alpha-methylbenzyloxy analogs, generated from the enantio-enriched stannanes via Sn/Li exchange, are shown to proceed predominantly with inversion of configuration at the Li-bearing terminus and retention of configuration at the migrating center, and exhibit a significant level of mutual enantiomer recognition in the radical recombination process.
(4) Asymmetric carbolithiative cyclization
The carbolithiative cyclization of enantiomerically-defined alpha-(homoallyloxy)stannane, with butyllithium is shown to proceed with complete retention of configuration at the Li-bearing center.