Abstract
A reaction of methyl (4R, 5R)-4, 5-epoxy-2(E)-hexenoate 1 with N-benzylmethylamine gave a diastereomerically pure methyl (4R, 5R)-4, 5-epoxy-(3S)-N-benzylmethylamino hexanoate 6 and methyl (4S, 5R)-4-N-benzylmethylamino-5-hydroxy-2(E)-hexenoate 7. The former was chemoenzymatically converted to (−)-osmundalactone 11, which is an aglycone of osmundalin. On the other hand, the directly conjugated addition of dimethylamine to methyl (4S, 5S)-4, 5-epoxy-2(E)-hexenoate 1 followed by treatment with MeOH at 40 °C exclusively provided methyl (4R, 5S)-4-dimethylamino-5-hydroxy-2(E)-hexenoate 16, which was converted into L-(−)-forosamine 18.
