SYNTHESIS OF PROVITAMINS D 



(S) 7-Dehydrosuosterol 



757 



The synthesis of 7-dehydrositosterol or provitamin D5 from sitosterol is 

 readily accomplished'^ by the Windaus method for 7-dehydrocholesterol. 

 Soybean oil is used as a source of sitosterol. 



c-o 



i ^ 



C.H,CO' 



CsKsCOCI 



w. 



wr 



KOH 



Fig. 4. The synthesi.s of 7-defiydrocholostcrol (XVII) from cholesterol (VI). 



(4) Oilier Provilamins D 



Epi-7-dehydrocholesterol can be produced by the Windaus method 

 for the preparation of 7-dehydrocholesterol, but using the epi-ckolesterol 



