An improved synthesis of azedarachol

An improved synthesis of azedarachol is reported in 10 steps with an overall yield of 12% from pregnanetriol. A proper use of p-anisaldehyde dimethyl acetal provided a chance of regioselective reduction of 2-enepregnane-16R,20R-p-anisaldehyde acetal(6) and in turn allowed a selective protection at C16-hydroxy and enabled a stereoselective reduction of C20-ketone to establish the configuration at C20.

Automated summary

An improved synthesis of azedarachol was reported, achieving an overall yield of 12% from pregnanetriol in 10 steps. The proper use of p-anisaldehyde dimethyl acetal allowed for a regioselective reduction of 2-enepregnane-16R,20R-p-anisaldehyde acetal (6), enabling the selective protection of C16-hydroxy and a stereoselective reduction of the C20-ketone to establish the configuration at C20.