Synthesis of new carbocyclic analogs of 1-(2′,3′-dideoxy-glycero-pentofuranosyl)pyrimidine nucleosides having the uracil (34), 2-thiouracil (33), 2-thiothymine (31), cytosine (44), and 5-methylcytosine (43) bases is described. The nucleoside analogs having the uracil, 2-thiouracil, and 2-thiothymine bases were prepared by couplingcis-3-aminocyclopentanemethanol (8) with 3-ethoxypropenoyl isocyanate (26), 3-ethoxypropenoyl isothiocyanate (25), and 3-methoxy-2-methylpropenoyl isothiocyanate (23), respectively, to give the corresponding acyl urea (30) and acyl thioureas (29and27). The acyl urea was cyclized in 2 NH2SO4and the acyl thioureas in 15 Naqueous ammonia to give the corresponding nucleoside analogs. The nucleoside analogs containing the cytosine (44) and 5-methylcytosine (43) bases were prepared from the uracil and thymine nucleoside analogs, respectively, by way of the 4-chloropyrimidinone intermediates (42and41). The synthesis ofcis-3-aminocyclopentanemethanol (8) from norbornene by way ofcis-1,3-cyclopentanedicarboxylic acid anhydride (3) is also described. In addition, the ease of nucleophilic opening of compound3is compared to the opening of camphoric anhydride (9), which contains acis-vicinal substituent at position 2. The relative ease of opening of compound3is discussed with respect to the effect, observed in an earlier study, that acis-vicinal acetoxy group has on the course of the nucleophilic opening of such anhydrides. The1H magnetic resonance spectra at 200 MHz of all of the synthetic intermediates and of the nucleoside analogs have been determined and discussed. The nucleoside analogs were screened for cell-growth inhibition using K-562 cells. Nucleoside analogs having the 2-thiouracil (33), 2-thiothymine (31), cytosine (44), and 5-methylcytosine (43) bases showed some growth inhibition with activity 150 to 300 times lower than that shown by 5-fluorouracil in this test system.