1,4‐Dihydrophthalazine‐1,4‐dione is used as diene protecting group in an efficient multistep procedure for the synthesis of the title compound (VIII) from the compound (I) derived from ergosterol.
A multistep procedure for the conversion of ergosterol into the tetrahydropyranyl ether of (24R)‐24,25‐dihydroxyprovitamin D3 using 1,4‐dihydrophthalazine‐1,4‐dione as diene protecting agent was compared with an established route, which uses 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione for the protection of the diene system. The disclosed reaction sequence allows to double the overall yield. The 1,4‐dioxo‐1,2,3,4‐tetrahydrophthalazin‐2,3‐ylene group proved to be the better diene protecting group in the ozonolytic degradation of the ergosterol side chain. Maintaining the protecting group in the next reaction steps offered further advantages by diminishing the air and light sensitivity of the intermediates.
Protection of the C6‐C7 double bond by 1,4‐dihydrophthalazine‐1,4‐dione as in the title compound (I) renders possible a nearly selective ozonolysis of the C‐17 side chain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.