Synthesis of (−)-astrogorgiadiol

Astrogorgiadiol is a naturally occurring Vitamin D analogue that, in cell culture, downregulates the production of the cytokine osteopontin (OPN). OPN has been implicated in virulent asthma, and OPN knockout mice do not develop osteoporosis. As we have pursued whole animal studies with astrogorgiadiol, we have increased the scale of the synthesis. We report an improved preparation of the A-ring synthon and the scale-up of the diasteromerically pure D-ring/sidechain chiron.