Synthesis of the diastereomers of dethiobiotin using the conjugate addition of 4-phenyloxazolidin-2-one to a nitroalkene

Natural D-dethiobiotin and its three stereoisomers were prepared from a sin gle nitroalkene 2. Conjugate addition of the potassium salt of (R)-4-phenyl oxazolidin-2-one 3 to 2 led to two diastereomeric nitro compounds 6 and 7. Their enantiomers were prepared from (S)-3. These compounds were converted in three analogous steps into the dethiobiotin isomers as their methyl este rs.