1',2'-SECOTHYMIDINES - THE PREPARATION OF 2,3'-ANHYDRO DERIVATIVES AND THE FORMATION OF 2 UNUSUAL DIMERIC PRODUCTS

2,2'- and 2,3'-anhydropyrimidine nucleosides are rigid compounds that are restricted to the syn conformation. In certain cases, this enforced conformational rigidity has led to biologically active compounds. To capitalize on this rationale, attempts were made to prepare the corresponding anhydro analogues of 1',2'-secothymidine. Starting with the functionalized butanetetrols and -triols (1a-c and 2a-c), derived from D-isoascorbic acid, the 1',2'-seco nucleoside tosylates 9a-c were prepared. While attempts to form the 2,3'-anhydro derivatives (10a and 12) were successful, no 2,2'-anhydro analogues could be obtained even under a variety of reaction conditions. Instead, unusual dimeric compounds were formed whose structures were confirmed by C-13 NMR and mass spectrometry. The dimerization reaction does not appear to have been previously reported.