| abstract |
This aplication provides a process for preparing enantiomerically pure .beta.-D-dioxolane nucleosides. In particular, a new synthesis of (-)-DAPD, suitable for large scale development, is described. In one embodiment the invention provides a process for preparing a substantially pure .beta.-D or .beta.-L-1,3-dioxolane nucleosides comprising a) preparing or obtaining an esterified 2,2-dialkoxy ethanol; b) cyclizing the esterified 2,2-dialkoxy ethanol with glycolic acid to obtain a 1,3-dioxolane lactone; c) resolving the 1,3-dioxolane lactone to obtain a substantially pure D- or L-lactone; d) selectively reducing and activating the D-or L-chiral lactone to obtain a substantially pure D- or L-1,3-dioxolane; e) coupling the D- or L-1,3-dioxolane to an activated and/or protected purine or pyrimidine base; and f) optionally purifiying the nucleoside to obtain a substantially pure protected .beta.-D or .beta.-L-1,3-dioxolane nucleoside. |