cycloguanil cycloguanil cycloguanil is a dihydrofolate reductase inhibitor, and is a metabolite of the antimalarial drug proguanil; its formation in vivo has been thought to be primarily responsible for the antimalarial activity of proguanil. however, more recent work has indicated that, while proguanil is synergistic with the drug atovaquone (as in the combination malarone), cycloguanil is in fact antagonistic to the effects of atovaquone, suggesting that, unlike cycloguanil, proguanil may have an alternative mechanism of antimalarial action besides dihydrofolate reductase inhibition. cycloguanilclinical dataatc codep01bb02 (who) identifiers iupac name 1-(4-chlorophenyl)-6,6-dimethyl-1,3,5-triazine-2,4-diamine cas number516-21-2 ypubchem cid9049chemspider8697 yunii26rm326wvnchemblchembl747 ycomptox dashboard (epa)dtxsid9022867 chemical and physical dataformulac11h14cln5molar mass251.72 g·mol−13d model (jsmol)interactive image smiles clc1ccc(cc1)n2c(=n/c(=n\c2(c)c)n)\n inchi inchi=1s/c11h14cln5/c1-11(2)16-9(13)15-10(14)17(11)8-5-3-7(12)4-6-8/h3-6h,1-2h3,(h4,13,14,15,16) ykey:qmnffxrfojiokz-uhfffaoysa-n y (verify) although cycloguanil is not currently in general use as an antimalarial, the continuing development of resistance to current antimalarial drugs has led to renewed interest in studying the use of cycloguanil in combination with other drugs. synthesis synthesis: patents: the reaction between 4-chloroaniline (1) and dicyandiamide (aka 2-cyanoguanidine) (2) gives 4-chlorophenylbiguanide (3). the condensation of this immediately with acetone to form the aminal cycloguanil (4).