The Mechanism Investigation in Substitution of 21-Bromo-3α-hydroxyl-3β-methoxymethyl-5α-pregnan-20-one with Nucleophile

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Title:	The Mechanism Investigation in Substitution of 21-Bromo-3α-hydroxyl-3β-methoxymethyl-5α-pregnan-20-one with Nucleophile
Authors:	(Chen, C.-Y.;);翁豐富(Wong, Fung Fuh)*;(Lee,Y.-H.);(Chou, S.-Y.;);(Huang, J.-J.;);(Yeh, M.-Y.)
Contributors:	藥學院藥物化學研究所
Date:	2006-11
Issue Date:	2009-08-26 16:27:16 (UTC+8)
Abstract:	A mechanistic study on the nucleophilic substitution of a strictly geometric 21-bromo- 3-hydroxyl-3-methoxymethyl-5-pregnan-20-one was described. Reaction of the - bromoketone with excess lithium imidazole followed by the addition of extra bases including n-butyllithium, methyllithium, lithium piperidine, and lithium pyrrolidine provided unexpected -nucleophilic carbonyl adducts that derived fromstrong base. Data from HPLC and proton NMR suggested an epoxide as the intermediate. Two possible reaction pathways were proposed for the nucleophilic substitution reaction. One pathway is the normal SN2 substitution reaction, directly provided the imidazoly product without the formation of the unexpected -substituted products. The other pathwaywent through an epoxide intermediate, in which imidazole anion or the strong bases addedwould attack fromthe less hindered site of the epoxide to give the substitution product.
Relation:	STEROIDS 71(11-12)942 ~948
Appears in Collections:	[Graduate Institute of Pharmaceutical Chemistry] Journal articles

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