How is Vitamin D3 butyrate (CAS: 31316-20-8) typically synthesized?

Vitamin D3 butyrate (CAS: 31316-20-8) is synthesized through a multi-step reaction where Vitamin D3 is esterified with butyric acid in the presence of a strong acid catalyst. The reaction involves butyric anhydride and Vitamin D3, followed by deprotonation with a base. The yield is typically around 85%, with good selectivity towards the butyrate esterification. This process requires careful control of temperature and concentration to ensure high purity and yield.