Styrene oxide as a stereochemical probe for the mechanism of aralkylation at different sites on guanosine.
The stereochemistry at the alpha-carbon atom of the styrene moiety in styrene oxide-guanosine products was established, and the stereochemical consequences of reaction of optically active styrene oxide with guanosine were investigated. Inversion of stereochemistry in products at the alpha-carbon of styrene oxide decreased in the sequence 7- much greater than N2- greater than O6-substituted guanosines. These findings show that an extensively ionized substrate is needed for reaction at the exocyclic N2 and O6 sites on guanosine but that the reactive intermediate is not an ideal planar trigonal carbonium ion. This follows because inversion exceeds retention in both of the exocyclic substituted products.
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Laboratory of Chemical and Physical Carcinogenesis, NCI-Frederick Cancer Research Facility, Maryland 21701.
Moschel
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RC
Hemminki
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Dipple
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D000478:Alkylation; D004852:Epoxy Compounds; D006151:Guanosine / Q000031:analogs & derivatives* / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D004852:Epoxy Compounds; D006151:Guanosine; C013690:styrene oxide