Asymmetric total synthesis, X-ray crystallography, and preliminary biological evaluation of 1-(1'-hydroxyethyl)-25-hydroxyvitamin D3 analogs of natural calcitriol

Article abstract of DOI:10.1021/jo00077a052

With 3-bromo-2-pyrone as diene and acrolein as dienothile, thermally mild Diels-Alder cycloaddition led to an isolable bicyclic lactone aldehyde that underwent highly stereocontrolled methyl Grignard addition to form essentially only a single diastereomer