Abstract: The combination of compounds of formula I and II can be used for the treatment of retroviraI infections. The combination can be used to treat AIDS and ARC and other diseases caused by the retrovirus HTV or other related viruses.

Abstract: Certain Castanospermine ester derivatives of the formula: ##STR1## wherein R, R.sub.1 and R.sub.2 are each independently hydrogen, C.sub.1-14 alkanoyl, C.sub.1-14 alkenoyl, cyclohexanecarbonyl, C.sub.1-8 alkoxyacetyl, ##STR2## naphthalenecarbonyl optionally substituted by methyl or halogen; phenyl (C.sub.2-6 alkanoyl) wherein the phenyl is optionally substituted by methyl or halogen; cinnamoyl; pyridinecarbonyl optionally substituted by methyl or halogen; dihydropyridine carbonyl optionally substituted by C.sub.1 -C.sub.10 alkyl; thiophenecarbonyl optionally substituted by methyl or halogen; or furancarbonyl optionally substituted by methyl or halogen; Y is hydrogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, halogen, trifluoromethyl, C.sub.1-4 alkylsulfonyl, C.sub.1-4 alkylmercapto, cyano or dimethylamino; Y' is hydrogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, halogen or it is combined with Y to give 3,4-methylenedioxy; Y" is hydrogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy or halogen; with R, R.sub.1 and R.sub.