3'/5'-regioselectivity of introduction of the 9-fluorenylmethoxycarbonyl group to 2'-o-tetrahydropyran-2-yl-nucleosidesand 2'o-(4-methoxytetrahydropyran-4-yl)-nucleosides - useful intermediates for solid-phase-rna-synthesis
Lehmann, C × Xu, Yz Christodoulou, C Gait, Mj Van Meervelt, Luc Moore, M Kennard, O #
X-ray structure analysis of the more laevorotatory isomers of 2'-O-tetrahydropyranyl-4N-benzoylcytidine (4b) and of 2'-O-tetrahydropyranyluridine (5b) confirmed their chirality at the satellite anomeric centre C2'' to be S. The other diastereomers (4a resp. 5a) exhibited an unexpected reversal of 3'/5'-regio-selectivity when treated with 9-fluorenylmethoxycarbonyl chloride in pyridine. The X-ray crystallographic results form the basis for a mechanistic proposal.