The synthesis of protected 1',2'-didehydro-2'-deoxyadenosines has been optimized by incorporating a phosphoranylidene protection of the adenine amino function. These unsaturated adenosines have served as substrates for the electrophilic iodopivaloyloxylation leading to new nucleosides modified at the anomeric position. Reaction of halopivaloates 10, 11 and 12 with tributyltin hydride generates indirectly C-1' radicals through a beta-(acyloxy)alkyl rearrangement. Rate constants for these rearrangements have been measured by using free-radical clock methodology and comparison of these data with previous reported results provides structural information about the nature of this important class of radicals. (C) 1997 Elsevier Science Ltd. All rights reserved.

The synthesis of protected 1',2'-didehydro-2'-deoxyadenosines has been optimized by incorporating a phosphoranylidene protection of the adenine amine function. These unsaturated adenosines have served as substrates for the electrophilic iodopivaloyloxylation leading to new nucleosides modified at the anomeric position. Reaction of halopivaloates 10, 11 and 12 with tributyltin hydride generates indirectly C-1' radicals through a $\beta$- (acyloxy)alkyl rearrangement. Rate constants for these rearrangements have been measured by using free-radical clock methodology and comparison of these data with previous reported results provides structural information about the nature of this important class of radicals.

The attempted intermolecular addition of malonyl radicals to 1',2'-unsaturated nucleosides has led to the unexpected formation of furanones. Thus, only catalytic amounts of ceric(IV) ammonium nitrate (CAN), induce a Ferrier rearrangement. The unsaturated lactone was isolated in good yield and can serve as a precursor for the synthesis of optically active products. (C) 1998 Elsevier Science Ltd. All rights reserved.

The attempted intermolecular addition of malonyl radicals to 1',2'- unsaturated nucleosides has led to the unexpected formation of furanones. Thus, only catalytic amounts of ceric(IV) ammonium nitrate (CAN), induce a Ferrier rearrangement. The unsaturated lactone was isolated in good yield and can serve as a precursor for the synthesis of optically active products.

The mechanism of 2-deoxyribonolactone formation from the reaction of photogenerated 2′-deoxyuridin-1′-yl radical with molecular oxygen in water has been investigated.

The title C-1' radical, obtained by photolysis of the corresponding tert-butyl ketone in water, was studied spectroscopically by EPR and laser flash photolysis methods and computationally.

The mechanism of 2-deoxyribonolactone formation from the reaction of photogenerated 2'-deoxyuridin-1'-yl radical with molecular oxygen in water has been investigated.

The title C-1' radical, obtained by photolysis of the corresponding tert-butyl ketone in water, was studied spectroscopically by EPR and laser flash photolysis methods and computationally. (C) 1998 Elsevier Science Ltd. All rights reserved.