Synthesis of (-)-5-amino-2(3,4-dimethoxyphenyl)-4-phenyl-1,3-dithiane

The key intermediate of the synthesis, the (1 R,2 S)-1-phenyl-2-phthalimido-1,3-propanedithiol ( 5) was prepared from the corresponding (1 S,2 S)-diol 1 in a six-step procedure. The absolute configuration of 5 followed from that of 4, which was established by X-ray crystallographic study. In reaction with veratraldehyde dithiol 5 was converted into 1,3-dithiane 6, isolated as a single isomer. The stereochemistry of the dithiane 6 was deduced from NMR spectral data analysis and MM calculations. Hydrazinolysis of 6 resulted in the title dithiane 7.