Stereoselective reduction of C-20 ketone of vitamin D CD-ring and a new synthetic approach to maxacalcitol

- We provided the (20S)- and (20R)-alcohols via the CBS stereoselective reduction.
- We developed a new synthetic approach to the 22-oxa-25-hydroxy Grundmann's ketone.
- A novel synthesis of maxacalcitol is achieved by the convergent Lythgoe coupling on gram scale.