A novel stereoselective synthesis of a chiral key intermediate for the preparation of vitamin D3

The cyclopentanone 3a, a key intermediate in the synthesis of vitamin D₃ and its metabolites, has been prepared in optical active form using(S)-γ-trityloxymethyl-γ-butyrolactone (6) as a chiral building block.     

A stereocontrolled partial synthesis of 1α-hydroxy vitamin D3

A novel and efficient partial synthesis of 1α-hydroxy vitamin D₃ ($\text{6}$), starting from 7-dehydrocholesterol ($\text{1}$), is reported. The crucial step in the synthesis involves a selective Diels-Alder reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with the 6,8-diene system of previtamin D₃ ($\text{3}$), generating an adduct $\text{7}$ suitable for the stereoselective introduction of the 1α-hydroxyl group. Cycloreversion of $\text{13}$ leads to the title compound.     

Stereoselective synthesis of Certonardolsterol D3

The first stereoselective synthesis of Certonardolsterol D₃ was described. Ene reaction and improved allylic oxidation were employed as key steps for efficient construction of the desired 3β,6α,15β-triol steroidal framework. The chiral side chain in Certonardolsterol D₃ was finally introduced by Julia olefination.     

An efficient synthesis of 1α, 25-dihydroxy vitamin D3

An efficient synthesis of the title compound is reported based on C-1 functionalization of the triazoline Diels-Alder adduct of 25-OH provitamin D₃ ($\text{2C}$).     

Synthese von 3-desoxy-3-amino-vitamin D3 und 3-desoxy-3-epiamino-vitamin D3 und D2

Vitamin D₂ and D₃ are transformed with triphenylphosphane-diethylazodicarboxylate-HN₃ into the epimeric azidoderivatives 1 and 3 with inversion of the configuration at C-3. Reduction with LiAlH₄ yields 3-desoxy-3-epiamino-vitamin D₂ and D₃2 and 4, which are characterized as their acetamides 2a and 4a. Furthermore epivitamin D₃-p-nitrobenzoate 5 is produced by reaction of vitamin D₃ with triphenyl- phosphanediethylazodicarboxylate-p-nitrobenzoic acid, which yields epivitamin D₃5a after saponification. Utilizing the same method as above leads with epivitamin D₃ to 5a 3-desoxy-3-azidovitamin D₃6, which is reduced to 3-desoxy-3-amino-vitamin D₃7 by LiAlH₄ and characterized as its acetamide 7a.     

The convenient route to cd fragment for the synthesis of vitamin D3 relatives

The efficient degradation of $\text{1}$ to the α-methylene ketone $\text{4}$ is described. Compound $\text{4}$ was then converted to the allylic alcohol $\text{8a}$ - the precursor of vitamin D³ relatives.     

Synthesis of prostaglandin D1 and D2 via the three-component coupling process

Facile, convergent entries to prostaglandin D₁ and D₂ are outlined.     

Novel regioselective C-6 and C-19 alkylation of vitamin D3 via its sulfur-dioxide adducts

Vitamin D-sulfur dioxide adducts undergo regioselective methylation at C-6 with sodium hydride used as the base and at C-19 with lithium tetramethylpiperidide. The methylated adducts are converted to the corresponding vitamin D derivatives by extrusion of sulfur dioxide.     

Synthesis of new vitamin D3 analogues with a decalin-type CD-ring

Vitamin D analogues, characterized by a decalin CD-ring fragment are described.     

Total synthesis of prostaglandin D1 methyl ester and 9-epi-prostaglandin D1 methyl ester

Synthesis of the title compounds are described via the dithiane enone (VIII); cuprate addition to (VIII) proceeds with asymmetric induction.     

Zur Bestimmung von Vitamin D2 und D3 in biologischem Material

Ohne Zusammenfassung     

lα-hydroxy previtamin D3, and its selective formation from 1-keto previtamin D3

An efficient method for the preparation of crystalline α-hydroxy previtamin D₃ is described. Also the stereoselective reduction of 1-keto previtamin $\text{9}$ is discussed; it was observed that with aluminum hydride $\text{7}$ is the most abundant product. This stands in contrast with previously reported LiAlH₄ and NaBH₄ mediated reductions.     

Facile, stereoselective synthesis of (24R)-24,25-dihydroxyvitamin D3 using D-glyceric acid as a chiral synthon

A facile, stereoselective, and efficient synthesis of (24R)-24,25-dihydroxyvitamin D₃, using D-glyceric acid as a chiral synthon to construct the side chain and ergosterol as a precursor of the secosteroid skeleton, is described.