Patent ID: 6930100

Claim:
A compound of the formula wherein the wavy bond ( ) represents the racemate, the (R)-enantiomer or the (S)-enantiomer; A is a direct bond or (C═O); B is a direct bond, oxygen or nitrogen; m is 0 or 1; n is 1, 2 or 3; R 1 and R 2 each are independently hydrogen, C 1-6 alkyl, benzyl, 4-methoxybenzyl, (lower)alkanoyloxy(lower)alkyl, (lower)alkoxycarbonyloxy(lower)alkyl, (lower)alkoxycarbonyl(lower)alkyl, (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl or dihydroxypropyl; and when R 1 is hydrogen, R 2 may also be —P(O)OR 5 OR 6 or heteroaryl; R 3 and R 4 each are independently hydrogen or C 1-4 alkyl; and R 5 and R 6 each are independently hydrogen, C 1-6 alkyl, benzyl, 4-methoxybenzyl, (lower)alkanoyloxy(lower)alkyl, (lower)alkoxycarbonyloxy(lower)alkyl, (lower)alkoxycarbonyl(lower)alkyl, (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl or dihydroxypropyl; or a nontoxic pharmaceutically acceptable salt or solvate thereof.