Reduction of tigogenin (la) and deoxytigogenin (lb) with lithium aluminum deuteride-aluminum chloride was shown to involve incorporation of hydride at the 22 position by an intermolecular mechanism. A possible alternative involving an intramolecular hydride shift from the 26 position was excluded. Position of the deuterium label was conclusively shown by pmr measurements and by chemical methods. An attempt to employ mass spectral evidence for assigning the deuterium position led to the observation of a rare seven-center transition state in an electron impact fragmentation sequence.
ASJC Scopus subject areas
- Organic Chemistry