Search

It was established that exclusively high regioselective C O bond cleavage of 7-oxabicyclo[2.2.1]heptane skeletons, which are unique Diels–Alder products of furans, under mild conditions using samarium(II) iodide and samarium powder yields cyclohexanol derivatives or aromatic compounds.

Selective oxidation of terminal isopropyl groups to the correspoding tertiary alcohols by an electrochemical method is described. Under the conditions using the Tl(TFA) 3 -hematoporphyrin-O 2 -cathodic reduction system, several substrates such as cholesterol ( 1 ) and Grundmann's alcohol ( 3 ) gave the corresponding tertiary alcohols 2 and 4 , respectively, in reasonable yield.

Stereoselective chlorination of cholesterol (1) was achieved by an electrochemical method to give a dichloride 2 and a cholohydrin 3. Using this procedure, blattelastanoside B (6), an aggregation pheromone of the German cockroach, was synthesized from β-sitosterol (5) in short steps.

The 7-oxa-2,3-dimethylenenorbornene derivative 3 , synthesized previously from 4 H ,6 H -thieno[3,4- c ]furan 5,5-dioxide ( 1 ) via its 2-acyl derivative 2 , readily rearranged to give 5 by treatment with Lewis acids in high yield.

Novel stereoselective method to introduce side chain onto 17-oxosteroids has been deviced, and using the method cholesterol and 25-hydroxycholesterol are synthesized.

24,24-Difluoro-25-hydroxyvitamin D3 ( 13 ) has been prepared from commercially available lithocholic acid derivative to study the role of 24-hydroxylation in the metabolism of vitamin D3.

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.

(25 R )-25,26-Dihydroxy-23-oxovitamin D 3 was synthesized efficiently and stereoselectively, and it was converted enzymatically to (25 R )-1α,25,26-trihydroxy-23-oxovitamin D 3 , a putative metabolite of 1α,25-dihydroxyvitamin D 3 . The spectral and chemical properties of (25 R )-25,26-dihydroxy-23-oxovitamin D 3 and its 1α,hydroxylated derivative disagree with those reported for the isolated metabolite.

25-Hydroxyvitamin D2 as synthesized conveniently and stereoselectively for the first time by utilizing Sharpless' chiral epoxidation and the subsequent regio- and stereoselective methylation with lithium dimethylcuprate to introduce the desired chirality at C(24) and the reductive elimination of the vicinal hydroxy sulfone to introduce stereoselectively the E double bond at C(22) of the target molecule.

Stereoselective synthesis of (25S)-25-hydroxyvitamin D3 26,23-lactone (1w) is described starting from C-22 steroidal aldehyde and (S)-citramalic acid. The spectral properties of the compound are almost identical with those of the natural product.

Stereoselective synthesis of (24R)-lα,24,25-trihydroxycholesterol (1a) from lα-hydroxydehydroepiandrosterone (5) was described, in which the C-20(R) and C-17(R) configurations were introduced by stereoselective conjugate addition of LiCuMe2 to sulfonylallene (15) followed by stereoselective reduction of 17(20)-dehydrosterol (19) and functionalities on the side chain were introduced by using chiral synthon (7).

A facile, stereoselective, and efficient synthesis of (24R)-24,25-dihydroxyvitamin D 3 , using D-glyceric acid as a chiral synthon to construct the side chain and ergosterol as a precursor of the secosteroid skeleton, is described.