A synthetic study of methyl 3-deoxy-3-fluoro-alpha-D-glucopyranosides from methyl 2,3-anhydro-alpha-D-allopyranosides, and synthesis of 3'-deoxy-3'-fluorokanamycin A and 3'-chloro-3'-deoxykanamycin A.

Reactions of 4,6-disubstituted 2,3-anhydro-alpha-D-allopyranosides with potassium hydrogenfluoride (KHF2) in ethane-1,2-diol gave, by oxirane-ring opening, the corresponding 2-deoxy-2-fluoro-alpha-D-altro- and 3-deoxy-3-fluoro-alpha-D-gluco-pyranosyl derivatives, with the latter always in preponderance. The influence of the substituents at C-4 and C-6 on the D-gluco-D-altro ratio (r) have been studied by molecular mechanics, and the discrepancy between the experimental and calculated r values has been positively utilized to measure the effects of solvation and hydrogen bonding relative to the C-4 and C-6 substituents. By application of this reaction, 3'-deoxy-3'-fluorokanamycin A has been prepared by treatment of a 2',3'-anhydro-3'-epikanamycin A derivative (35) with KHF2. 3'-Chloro-3'-deoxykanamycin A was also prepared.