O-Phosphonatomethylcholine, its analogues, alkyl esters, and their biological activity

O-Phosphonatomethylcholine, an isopolar phosphocholine analogue with a phosphonomethyl ether group replacing a phosphomonoester residue, was prepared by reaction of diisopropyl 2-chloroethoxymethylphosphonate with dimethylamine followed by quaternization of the thus-obtained diisopropyl 2-dimethylaminoethoxymethylphosphonate with iodomethane; the ester groups in the quaternary intermediate were cleaved with bromotrimethylsilane. Replacement of dimethylamine in the reaction sequence by morpholine and/or pyrrolidine gave the N-methylmorpholinium or N-methylpyrrolidinium analogues of O-phosphonatomethylcholine. Reaction of O-phosphonomethylcholine monotetrabutylammonium salt with 1-bromoalkanes in acetonitrile afforded a series of the corresponding monoalkyl (C10-C16) esters. None of these compounds except for the hexadecyl ester exhibited any appreciable cytostatic activity against DU-145, H460, HT-29, or MES-SA cell lines in vitro (evaluated by 3H-Thd incorporation assay). The hexadecyl ester exhibited modest in vitro cytotoxic activity comparable to that of the anticancer drug miltefosine (hexadecyl O-phosphocholine). In vivo evaluation of hexadecyl O-phosphonomethylcholine [transplanted SD lymphoma in inbred SD/cub rats, 10 mg kg(-1) day(-1) intratumoral injection for 10 days] resulted in a 40% decrease in lymphoma mass.