Compounds 396-398

protection of the 2-N-ferf-butoxycarbonyl group followed by formimidation of the 2"-amino function with ethylformimidate hydrochloride and deprotection of the protecting groups led to the formation of the title compounds. These naturally occurring aminoglycosides have strong antibacterial activity, similar to istamycin A and B

A number of istamycin B analogs, including 5-epi-, 3-O-demethyl-5-epi-, 3-O-demethyl-3-epi-, 3-demethoxy, 3-demethoxy-2"-N-formimidoyl [240], 3-O-demethyl, and several 2'-N-acyl and N-amidinyl [241] derivatives have been synthesized. Of these, the 3-demethoxy and 3-demethoxy-2"-N-formimidoyl analogs showed more potency than istamycin B and its 3-O-demethyl derivative.

Various istamycin derivatives (compound 405) bearing different aminoacyl groups at the 4-amino group have been synthesized. These analogs, which have a combination of hydroxyl and amino groups for X and Y in their structures [e.g., (X, Y) = (NH2, OH), (OH, OH), (H, OH), (OH, NH2)], showed promising antibiotic activity. Of these, the antibiotic (compound 406) was tested with 54 bacteria and showed potent antibacterial activity, much higher than that of istamycin B [242].

3. Sporaricins

The three fluorinated derivatives of sporaricin A 407, including 3-demethoxy-3-fluoro (408), 3-demethoxy-epi-fluoro (409), and 3-demethoxy-3,3-difluoro (410), have been prepared from a protected 3-demethylsporaricin derivative. Direct fluorination of the



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