Formycin analogs. I. Model studies in the preparation of an isomer of formyein and related derivatives (s-triazolo[4,3-a] pyrazines)

The synthesis of a number of 8-substituted- and 3-methyl-8-substituted-.s-triazolo4,3-a]-pyrazines as model molecules for an isomer of formyein (i.e., 8-amino-3-(β-D-ribofuranosyl)-s-triazolo4,3-a ]pyrazine ( 2 )) and some of its derivatives (including aglycone) is reported. The C-8 subslituents include amino ( 3a and 4a ), chloro ( 3b and 4b ), hydroxy (as the 8 -ones 8a and 9a ), mercapto (as the 8 -thiones 8c and 9c ), hydroxylamino ( 3e and 4e ), selenoxy (as the 8 -selenones 8d and 9d ), metlioxy ( 3g and 4g ), and thiomethoxy ( 3h and 4h ). Also described are 7-methyl-s-triazolo4,3-a]pyrazin-8(7H) one ( 8b ) and its 3-methyl derivative ( 9b ) together with imidazo1,2-g]-s-triazolo4,3-a]pyrazine ( 10a ) and its 3-methyl derivative ( 10b ). Complete spectral data for all of these molecules is presented.