ACYCLIC-SUGAR PURINE NUCLEOSIDES DERIVED FROM D-GLUCOSE: STEREOCHEMICAL CORRELATIONS IN ACYCLIC-SUGAR DERIVATIVES UNEQUALLY SUBSTITUTED AT C1

Article abstract of DOI:10.1016/S0008-6215(00)84863-6

Condensation of 2,3,4,5,6-penta-O-acetyl-1-bromo-1-S-methyl-1-thio-D-glucitol (1) with 6-chloro-9-(chloromercuri)purine gave 49percent of crystalline, levorotatory (1S)-2,3,4,5,6-penta-O-acetyl-1-(6-chloropurin-9-yl)-1-S-methyl-1-thio-D-glucitol (3), together with a smaller proportion of the syrupy, dextrorotatory (1R) isomer.Thiourea converted 3 into its 6-mercaptopurine analog, whose O-deacetylated derivative could be S-methylated to the corresponding 6-(methylthio)purin-9-yl analog: all compounds in this sequence were crystalline and were the pure (1S) isomers, as were the corresponding 1'-S-ethyl derivatives prepared by a similar route.Crystal-structure analysis of the O-deacetylated derivative of the 1'-S-ethyl analog of 3 established the relative stereochemistry of the ethyltio group, permitting assignment of the (1S) absolute stereochemistry to this compound and thus to all compounds in the sequence starting from 1, including the previously described, crystalline, levorotatory 1-(1,6-dihydro-6-thioxopurin-9-yl)-1-S-ethyl-1-thio-D-glucitol, whose chirality at C-1 had not hitherto been established.The close similarity of the chiroptical properties of the crystalline 1'-S-methyl derivatives to those of their 1'-S-ethyl counterparts permitted firm attribution of (1S) chirality to the former series also.Conformational studies showed that all of the derivatives have the sugar chain in a non-extended (sickle) conformation.