Novel synthesis of 1- and 3-epi-tobramycin and 1-epi-kanamycin A - Igarashi, K.; Sugawara, T.; Honma, T.; Tada, Y.; Miyazaki, H.; Nagata, H.; Mayama, M.; Kubota, T. (Elsevier)
Electrochemical reduction of 1-deamino-3,2',6',3''-tetra-N-formyl-1-hydroxyiminotobramycin (4) and 1-deamino-3,6',3''-tri-N-formyl-1-hydroxyiminokanamycin A (5) (prepared in good yields by oxidation of the corresponding amines with hydrogen peroxide in the presence of a catalytic amount of sodium tungstate), by using a mercury cathode at -1.85 volt (vs. a saturated calomel electrode) gave principally 1-epi-tobramycin (6) and -kanamycin A (7) derivatives. Similar results were obtained by catalytic hydrogenation of 4 and 5 over Raney nickel. The electrochemical reduction or catalytic hydrogenation of 3-deamino-1,2',6',3''-tetra-N-formyl-3-hydroxyiminotobramycin (17) gave mainly the corresponding tobramycin derivative. Reduction of 4 and 17 with sodium cyanoborohydride gave principally the corresponding 1-epi-1- and 3-epi-3-hydroxyamino derivatives. Hydrogenation of these over Raney nickel gave the corresponding amines in quantitative yields. Hydrolysis of 1- and 3-epi-tobramycins with 48% hydrobromic acid under reflux gave (1l-1,3,42,6-4,6-diaminocyclohexanetriol, [α]^2^1^.^5"D +39.4^o and (1d)-1,3,42,6-4,6-diaminocyclohexanetriol, [α]^2^4"D -37.0^o, respectively.
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