Metal-Dependent Reaction Tuning with Cyclopentylmetal Reagents: Application to the Asymmetric Synthesis of (+)-α-Conhydrine and (<i>S</i>)-2-Cyclopentyl-2-phenylglycolic Acid
The reaction of halocyclopentane organometallic reagents can be tuned by the choice of metal (see scheme). Cyclopentylmagnesium bromide reduces aldehydes and ketones to the corresponding alcohols. However, in the presence of ZnCl2, normal Grignardaddition to the ketones gives tertiary alcohols with complete diastereoselectivity. These protocols were used in the asymmetric synthesis of two medicinally
A general and concise stereodivergent chiral pool approach toward trans-(4S,5R)- and cis-(4R,5R)-5-alkyl-4-methyl-γ-butyrolactones: Syntheses of (+)-trans- and (+)-cis-whisky and cognac lactones from d-(+)-mannitol
A straightforward synthesis of (+)-trans-(4S,5R)- and (+)-cis-(4R,5R)-whisky lactones starting from d-(+)-mannitol has been reported here in fewer number of efficient steps compared to existing literature processes involving d-mannitol as the chiral pool starting material. Chiron approach directly translated chirality of d-mannitol to one of the two chiral centers in these target molecules. Toward
从d -(+)-甘露醇开始直接合成 (+)-反式-(4 S ,5 R )- 和 (+)-顺式-(4 R ,5 R )-威士忌内酯的报道较少与涉及d-甘露醇作为手性池起始材料的现有文献方法相比,有效步骤的数量。Chiron 方法直接将d-甘露醇的手性转化为这些靶分子中的两个手性中心之一。为此,立体异构纯的反式和顺式在倒数第二步中形成碘甲基-γ-内酯。这两种作为通用的高级通用中间体也分别转化为 (+)-反式-(4 S ,5 R )- 和 (+)-顺式-(4 R ,5 R )-干邑内酯。据我们所知,迄今为止还没有报道从d-甘露醇开始合成干邑内酯。所有这些内酯都被确定为陈年酒精饮料的关键香气成分。
(R)-2,3-O-Cyclohexylideneglyceraldehyde, a Versatile Intermediate for Asymmetric Synthesis of Chiral Alcohol
作者:A. Chattopadhyay、V. R. Mamdapur
DOI:10.1021/jo00108a020
日期:1995.2
Grignard addition to (R)-2,3-O-cyclohexylideneglyceraldehyde (IIa) gave rise to column chromatographically separable diastereo alcohols 2 and 3 including highly functionalized and synthetically exploitable homoallylic alcohols 2e and 3e and homopropargylic alcohols 2f and 3f. Compound 3c on functional manipulation gave rise to (-)-coriolic acid synthon 6.
Chattopadhyay A., Mamdapur V. R., J. Org. Chem, 60 (1995) N 3, S 585-587