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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/11735

Title: Highly stereoselective synthesis of spiro-alpha-methylene-gamma-butyro-lactones: the role of alpha-hydroxy substitution
Authors: SAWANT, MS
KATOCH, R
TRIVEDI, GK
DESAI, UR
Keywords: controlled nucleophilic additions
crotyltri-n-butylstannane
sesquiterpene lactones
asymmetric induction
reformatsky reagent
carbonyl-compounds
effective system
chelation
organometallics
alkoxyaldehydes
Issue Date: 1998
Publisher: ROYAL SOC CHEMISTRY
Citation: JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1, (5), 843-846
Abstract: An alpha-alkoxy substituent provides acceleration and greater diastereoselectivity in organometallic additions to chiral ketones. We find that alpha-hydroxy substitution also plays a similar role. Whereas the addition of a Reformatsky reagent to unsubstituted steroidal ketones does not yield the desired products, alpha-hydroxy substitution provides the alpha-methylene-gamma-butyrolactone steroid in good yields and very high diastereoselectivity. The alpha-methylene-gamma-butyrolactone moiety has been synthesized at several positions on the steroid nucleus. The stereochemistry can be explained through a chelated transition state, while the enhancement in the rate may be due to both the electron-withdrawing nature of the Reformatsky reagent and the neighbouring group effect.
URI: http://dx.doi.org/10.1039/a708558c
http://dspace.library.iitb.ac.in/xmlui/handle/10054/11735
http://hdl.handle.net/10054/11735
ISSN: 0300-922X
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