SYNTHESIS, PROPERTIES AND MICROBIOLOGICAL ACTIVITY OF HYDROPHOBIC DERIVATIVES OF VITAMIN-B-12

Long chain alkylcobalamins and long chain acyl-cyanocobalamins, two ty pes of hydrophobic derivatives of vitamin B-12, were synthesized. It w as shown by TLC and determination of the partition coefficient between organic and aqueous phases that the hydrophobicity of alkylcobalamins and acyl-cyanocobalamins increased with the chain length of the alkyl or acyl group introduced into cobalamin. Long chain alkylcobalamins w ere easily converted to aquacobalamin by photoirradiation, but the fir st-order rate constant of photolysis decreased with the length of an a lkyl group. Long chain acyl-cyanocobalamins were gradually hydrolyzed to cyanocobalamin in neutral or alkaline solution with the pseudo-firs t order rate constant increasing with the pH of the solution. Stabiliz ation of acyl-cyanocobalamins toward hydrolysis was achieved by introd ucing a methyl group into the alpha-position of an acyl group. All the long chain alkylcobalamins tested supported the growth of Escherichia coli 215, a cobalamin- or L-methionine-auxotroph, and Lactobacillus l eichmannii, although their activity as cobalamin was at most 28% and 1 5% that of cyanocobalamin for E. coil 215 and L. leichmannii, respecti vely.