Synthesis of acyclo C-nucleosides: sterically controlled regiospecific heterocyclization of aldehydo-sugar {5-methyl-1,2,4-triazino[5,6-b]indol-3-yl}-hydrazones to 3-(alditol-1-yl)-10-methyl-1,2,4-triazolo[4 ' 3 ': 2,3]1,2,4-triazino[5,6-6]-indoles

Condensation of 3-hydrazino-5-methyl-1,2,4-triazino[5,6-b]indole (1) with m onosaccharides 2a-g gave the corresponding aldehydo-sugar hydrazones 3a-g w hich were acetylated to the corresponding hydrazone acetates 4a-g. The latt er underwent sterically controlled regiospecific oxidative cyclization with bromine in acetic acid and in the presence of sodium acetate to the linear ly annulated 3-(poly-O-acetyl-alditol-1-yl)-10-methyl-1,2,4-triazolo[4',3' :2,3]1,2,4-triazino[5,6-b]indoles 8a-g rather than to the angularly annulat ed regioisomers 6. The regiospecific outcome of this heterocyclization has been discussed in terms of electronic and steric factors and the assigned s tructure 8 has been corroborated on the basis of chemical as well as spectr al evidence. De-O-acetylation of 8a-g with ammonium hydroxide in methanol g ave the title acyclo C-nucleosides 9a-g. Representative members of the prep ared compounds were tested for antimicrobial activity.