Industrial-scale synthesis of eldecalcitol is described. AA highly diastereoselective epoxidation of p-methoxybenzyl (PMB) protected dienol at room temperature provides the key epoxide intermediate with a secondary hydroxyl group, which is alkylated with a triflate to set up all of the subunits at the C-1, C-2, and C-3 positions of the A-ring fragment. Selective protecting group manipulation followed by palladium-catalyzed cyclization then provides the A-ring synthon. The C/D-ring fragment is obtained by (1) direct C-H hydroxylation of Grundman's ketone using in situ prepared trifluoropropanone dioxirane and (2) protection. Finally, the coupling of the A-ring with the C/D-ring fragment, global deprotection, and recrystallization provide the highly crystalline eldecalcitol.

A highly convergent, gram-scale synthesis of vitamin D3 analogue tacalcitol 1 is disclosed, starting from L-valine and Inhoffen–Lythgoe diol. Key features of the synthesis include modified Julia olefination reaction of β-oxybenzothiazol-2-yl sulfone with C/D ring containing aldehyde to access decagrams of fully functionalized C/D ring synthon. The Horner–Wadsworth–Emmons (HWE) reaction between the C/D ring fragment and commercially available phosphonate completes the carbo-skeleton, which is elaborated into tacalcitol 1 in a gram-scale synthesis.

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