Abstract: Compounds of formulae ##STR1## wherein X is O;R.sup.1 is OH, phosphate, diphosphate, triphosphate or (CH.sub.2).sub.n --O--CH.sub.2 --O--P(.dbd.O)(OH).sub.2 wherein n is 0-2;R.sup.2 is H and R.sup.3 is CH.sub.3, CH.sub.2 OH, CH.sub.2 --O--CH.sub.3, CH.sub.2 SH, CH.sub.2 F or CH.sub.2 N.sub.3 ; orR3 is H and R.sup.2 is CH.sub.3, CH.sub.2 OH, CH.sub.2 --O--CH.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;are synthesized from acyclic intermediates and are subsequently useful in the preparation of nucleoside analogues with antiviral activity against retroviruses such as HIV and hepatitis B.

Abstract: A process for preparing S-metoprolol of the formula ##STR1## or a salt thereof, with high enantiomeric purity, is described, whereby a (S)-5-hydroxymethyl-3-isopropyloxazolidin-2-one sulfonic acid ester of the formula ##STR2## is prepared, and further reacted with 4-[2-methoxyethyl]phenol of the formula ##STR3## and the resulting intermediate of the formula ##STR4## is hydrolysed to S-metoprolol, and whereby the (S)-5-hydroxymethyl-3-isopropyloxazolidin-2-one sulfonic acid ester of formula II is prepared by reacting (S)-3-isopropylamino-1,2-propanediol of the formula ##STR5## with a chloroformic acid ester of the formula ##STR6## wherein R' is an alkyl group having 1-3 carbon atoms or a phenyl group, to the formation of (S)-5-hydroxymethyl-3-isopropyloxazolidin-2-one of the formula ##STR7## which is reacted with an activated sulfonic acid of the formula ##STR8## wherein R" is an aryl group such as tolyl and X is a halogen such as Cl, to formation of the ester of formula II, which when required is enriched wit