Synthesis of furanosyl compounds useful as intermediates in preparation of nucleoside analogues

A process for preparing a compound of the formula ##STR17## wherein X is O;

• R.sup.1 is OH, O--PO(OH).sub.2, O--PO(OH)--O--PO--(OH).sub.2, O--PO(OH)--O--PO(OH)--O--PO(OH).sub.2, or (CH.sub.2).sub.n OCH.sub.2 PO(OH).sub.2 where n is 0-2;
• R.sup.2 is H and R.sup.3 is CH.sub.3, CH.sub.2 OH, CH.sub.2 OCH.sub.3, CH.sub.2 SH, CH.sub.2 F or CH.sub.2 N.sub.3 ;
• and
• Z is Cl, Br, I, acyloxy or alkoxy;
• which process comprises reacting a protected butan-1,4-diol-2,3-epoxide of the formula ##STR18## wherein R.sup.8 is a protecting group or hydrogen, and R.sup.9 is a protecting group, with an alpha allylic nucleophile to produce a 2-hydroxy, 3-allyl, butane-1,4-diol,
• optionally protecting the 4-alcohol group when R.sup.8 is hydrogen, oxidatively cleaving the double bond in the 3-allyl group to produce an aldehyde which will ring close with the 2-hydroxyl group;
• and
• halogenating, acylating or alkoxylating the resulting furanose.