Sterically controlled regiospecific cyclization of aldose-5-ethyl-1,2,4-triazino[5,6-b]indol-3-ylhydrazones to linearly annelated 3-polyhydroxyalkyl-10-ethyl-1,2,4-triazolo-[4 ',3 ': 2,3]-1,2,4-triazino[5,6-b]indoles

Condensation of aldoses with 5-ethyl-3-hydrazino-1,2,4-triazino[5,6-b]indol e gave the corresponding aldose-5-ethyl-1,2,4-triazino[5,6-b]indol-3-ylhydr azones which were acetylated to their poly-O-acetyl derivatives. The latter underwent sterically controlled regiospecific oxidative cyclization with b romine in acetic acid and sodium acetate to sterically favourable linearly annelated 3-polyacetoxyalkyl-10-ethyl-1,2,4-triazole[4',3':2,3]-1,2,4-triaz ino[5,6-b]indoles rather than to their sterically unfavourable angularly an nelated regioisomers. The regiospecific outcome of this heterocyclization i s discussed in terms of electronic as well as steric factors, and the assig ned structures have been corroborated on the basis of chemical as well as s pectroscopic evidence. De-O-acetylation of the acetoxyindoles with ammonium hydroxide in methanol gave the title compounds. Representative members of the prepared compounds were tested for antimicrobial activity.