A series of xanthine derivatives in which a methylene was inserted at position 8 of xanthine scaffold was synthesized and evaluated as inhibitors of dipeptidyl peptidase 4 (DPP-4) for the treatment of type 2 diabetes. As the results of structure–activity relationship (SAR) study of the series, the compounds with 4-methyl-quinazoline-2-yl-methyl group at N-1 position and 2-aminoethylaminomethyl group gave better activities. Compounds H4 and H9 showed good DPP-4 inhibition and more than 100-fold selectivity over DPP-7 and DPP-8.

A series of novel 5'-deoxy-4'-thio-L-nucleosides was designed and synthesized. The absolute configuration of the target compound 23alpha was confirmed by X-ray crystallography. The antitumor activities of the target compounds were tested against the growth of human carcinoma of colon (LOVO), human leukemia cell line (CEM) and human breast cancer cell line (MDA-MB-435) cells in vitro. 6-cyclopentylamino and 6-cyclohexylamino purine compounds 26 and 27, both in alpha-configuration and in beta-form, exhibited strong inhibition to CEM.