SYNTHESIS OF PURINE DERIVATIVES AS POTENTIAL ANTITHYROID AGENTS

Abstract

Various purine derivatives mainly 6 and 8-substituted sulfanylpurines were synthesized and evaluated for their potential antithyroid activity. The basic theme of the research work originated from the idea of combining the two most popular existing antithyroid drugs, namely propylthiouracil (1) and methimazole (2), into a single molecule to get the combined effect of both drugs through a single compound. Interestingly it resulted in 2,8-disulfanyl-1,9-dihydro-6H-purin-6-one (86). The compound was prepared using known method and three major series along with some individual compounds were also synthesized because the structural properties of the purines and their ability to complex with molecular iodine made them potential antithyroid compounds. In this regard, a series of 8-(alkylsulfanyl)-3,9-dihydro-1H- purine-2,6-diones (144-148) was synthesized using 8-sulfanyl-5,9-dihydro-1H-purine- 2,6-dione (84) and respective alkyl halides in aqueous solution; a second series of 6- (Alkylsulfanyl)-9H-purines (149-159) was synthesized using 6-sulfanylpurine monohydrate and respective alkyl halides in aqueous sodium hydroxide solution. Similarly, ethyl (9H-purin-6-ylsulfanyl)acetate (162) was synthesized using 6- sulfanylpurine monohydrate, triethylamine and ethyl chloroacetate in ethanol and 2-(9H- purin-6-sulfanyl)acetohydrazide (163). Ethyl (9H-purin-6-sulfanyl)acetate (162) and hydrazine hydrate were refluxed in ethanol to get the desired product. Both conventional and microwave assisted methods were used. Microwave assisted heating reduced the reaction time and improved the yield. A series of N'-[Substituted phenylmethylidene]-2- (79-purin-6-sulfanyl)acetohydrazides (164-172) was also synthesized by heating 163 and substituted benzaldehydes in ethanol under reflux. The compounds were studied in vitro as well as in vivo for determining their antithyroid effects. Fortunately, most of them showed significant antithyroid activity with a few to be exceptionally good in this respect. The successful exposition of the synthesized compounds endorsed the idea of the research programme. It is certainly not the end but a new start. The 6 and 8 substituted purine derivatives may now be categorized as a new class of antithyroid agents. These compounds can be used as alternate drugs for popular benefit after completing the requisite procedures like evaluation of cytotoxicity, determining metabolic route and clinical trial etc.