- C-5 Modified nucleosides: Direct insertion of alkynyl-thio functionality in pyrimidines
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A route is presented to append, in a single step, alkynyl thioesters to the 5-position of a pyrimidine ring of a nucleoside that is unprotected. These products should be useful to support in vitro selection experiments with functionalized DNA.
- Held, Heike A.,Roychowdhury, Abhijit,Benner, Steven A.
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- Attempts at vinyl radical carbonylation through cyclization onto carbonyl and cyano groups
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Sulfanylvinyl radicals 4-6, 16, produced from toluenesulfanyl radical addition to alkynes 1-3, 15, gave only products arising from cyclization onto the thiophenyl ring and H-abstraction. No products were obtained deriving from possible 5-membered cyclization onto the esteric or thioesteric carbonyl group. Similar results were obtained from toluenesulfanyl radical addition to alkynyl nitriles 20 and 24, which did not provided any evidence for 5- or 6-membered vinyl radical cyclization onto the aliphatic cyano group. In contrast, both toluenesulfanyl- and benzenesulfanyl- vinyl radicals 32 and 37a smoothly cyclize onto the aromatic cyano group leading to ketones 35 and 39. This protocol represents a novel indirect radical carbonylation and provides a useful synthetic approach to indenones.
- Montevecchi, Pier Carlo,Navacchia, Maria Luisa,Spagnolo, Piero
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p. 8207 - 8216
(2007/10/03)
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