| Abstract
| - Treatment of protected 2‘-deoxy-3‘,4‘-unsaturated nucleosides derived from adenosine and uridine withdifluorocarbene [generated from bis(trifluoromethyl)mercury and sodium iodide] gave fused-ring 2,2-difluorocyclopropane compounds. Stereoselective α-face addition to the dihydrofuran ring resulted fromhindrance by the protected β-anomeric nucleobases. A protected uracil compound was converted smoothlyinto the cytosine derivative via a 4-(1,2,4-triazol-1-yl) intermediate. Removal of the protecting groupsgave new difluorocyclopropane-fused nucleoside analogues. The solid-state conformation of the nearlyplanar furanosyl ring in the uracil compound had a shallow 2E pucker, and a more pronounced 1Econformation was present in the furanosyl ring of the cytosine derivative.
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