Chemical modification of an antitumor alkaloid, 20(S)-camptothecin: glycosides, phosphates and sulfates of 7-ethyl-10-hydroxycamptothecin.

Water-soluble derivatives having the lactone ring intact were synthesized starting from 7-ethyl-10-hydroxycamptothecin (1). Glycosides (2) of the phenolic hydroxyl group of 1 were obtained by reaction with acetylated alpha-bromosugars in acetone or aqueous acetone in the presence of potassium carbonate, followed by deprotection. Phosphates (3) were prepared by reaction of 1 with phosphoryl chloride in pyridine or with dibenzylchlorophosphoridate. Sulfates (4) were obtained by reaction of 1 with sulfur trioxide-pyridine complex in the presence of a tertiary amine. The organic ammonium salts of monophosphate (3p) and sulfates (4a and 4b) showed significant activity against L1210 in vivo.