Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

Rhodium-catalyzed intramolecular reductive aldol-type cyclization was described to give β-hydroxylactones with high diastereoselectivities. This cyclization gave syn - or anti -form β-hydroxylactones selectively by changing the solvent. Furthermore, the synthesis of a chiral necic acid lactone was also described which is a part of structural component of pyrrolizidine alkaloid monocrotaline that is used for the preparation of pulmonary hypertension pathological model in rats.