Antonio Rumbo

Use of a sulfinyl tether to control diastereofacial selectivity in [5C + 2C] pyrone-alkene cycloadditions

Abstract The incorporation of a sulfoxide on the tether connecting an alkene to a 5-silyloxy-4-pyrone diminishes the temperature needed for inducing their thermal [5C+2C] cycloaddition in relation to that required for annulating the homologous sulfide, and allows for attaining modest levels of diastereofacial selectivity.

Stereoselective synthesis of C24-hydroxylated vitamin D3 analogs: a practical and expeditius route to calcipotriol.

The synthesis of the clinically important drug calcipotriol (2, MC903) is described as an example of a new and efficient approach to C24-hydroxylated analogs and metabolites of vitamin D3 (1). The key step of the process is the generation of the C24 stereocenter by DAIB [(-)-3-exo-(dimethylamino)isoborneol]-catalyzed addition of the alkenylzinc derivative of alkyne 3 to cyclopropylcarboxaldehyde.