Abstract: wherein Z1 is hydrogen or an amino-protecting group selected from the group consisting of acyl of the formula R—C(O)—, wherein R is alkyl of 1-6 carbon atoms; trityl, optionally substituted with methoxy; and N-(9-fluorenylmethoxycarbonyl); Y1 is halo, aralkyloxy or acyloxy, wherein acyl is as defined above; and Y2 is aralkyloxy. These intermediates are useful in a novel process for preparing the mono-L-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl) methoxy-1,3-propanediol (ganciclovir). The mono-L-valine ester of ganciclovir and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: Process for preparing intermediates of formula (III) wherein Y1 is acyloxy, wherein acyl is of the formula R—C(O)—, wherein R is alkyl of 1-6 carbon atoms, Y2 is aralkyloxy, and Z is benzoyloxy or acyloxy, wherein acyl is as defined above. Intermediates of formula (III) are useful in a novel process for preparing the mono-L-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol (ganciclovir). The mono-L-valine ester of ganciclovir and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: Intermediates of Formula (III) wherein Y1 is acyloxy, wherein acyl is of the formula R—C(O)—, wherein R is alkyl of 1-6 carbon atoms, Y2 is aralkyloxy, and Z is benzoyloxy or acyloxy, wherein acyl is as defined above. Intermediates of formula (III) are useful in a novel process for preparing the mono-L-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol (ganciclovir). The mono-L-valine ester of ganciclovir and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: Intermediates of Formula (III) ##STR1## wherein P.sup.1 is hydrogen or an amino-protecting group, R is lower alkyl, allyl or aralkyl, and Z is hydrogen, lower alkyl, aryl or aralkyl; and Formula (VI) ##STR2## wherein P.sup.1 is hydrogen or an amino-protecting group, P.sup.2 is an amino protecting group, and Z is hydrogen, lower alkyl, aryl or aralkyl, are useful in a novel process for preparing the mono-L-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol (ganciclovir). The mono-L-valine ester of ganciclovir and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: Process and novel intermediates for preparing the L-mono-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol and its pharmaceutically acceptable salts. The present process and intermediates provide for reduced impurities in the mono-valine ester end-product and lower overall production costs. The process involves the condensation of a silylated guanine compound with a substituted glycerol derivative and esterification of this product with an L-valine derivative. These mono-valine products are of value as antiviral agents with improved absorption.

Abstract: An .omega.-guanidino-.alpha.-amino-acid (or its functional derivative) or a compound containing it may be prepared by the reaction of the .omega.-amino group of an .alpha.,.omega.-diamino acid (or its functional derivative) or a compound containing it with a formamidinesulfonic acid.

Abstract: Process and novel intermediates for preparing the mono-L-valine ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol ganciclovir) and its pharmaceutically acceptable salts. The present process and monoester intermediates provide for mono-esterification by an L-valine derivative, resulting in a monocarboxylate-monovalinate which is then selectively hydrolyzed under basic or enzymatic conditions to give the monovaline ester of ganciclovir in high yield and purity. These products are of value as antiviral agents with improved absorption.

Abstract: Process for preparing the L-monovaline ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol and its pharmaceutically acceptable salts. The present process provides an N,O-bis-trityl intermediate of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol which allows for mono-esterification by an L-valine derivative. These products are of value as antiviral agents with improved absorption.

Abstract: Process for preparing the L-monovaline ester of 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol and its pharmaceutically acceptable salts. The present process relates to an improved process whereby ganciclovir is esterified with an L-valine derivative to provide a di-valine ganciclovir intermediate. Removal of one of the valine groups with a lower alkyl amine, benzylamine or benzyl methylamine provides the mono-valine ester compound of Formula I. These products are of value as antiviral agents with improved absorption.