A-ring Synthon Research Articles

A novel highly stereoselective synthesis of the A-ring of taxol via two aldol reactions

An efficient, scalable route to the Taxol A-ring synthon is described; high stereoseiectivity and regioselectivity are achieved by means of an intermolecular Aldol addition and an intramolecular Aldol condensation.

A practical asymmetric synthesis of a 1,7-enyne A-ring synthon en route toward the total synthesis of vitamin D 3 analogues

A concise synthesis of a key A-ring synthon of 1α,25-dihydroxyvitamin D 3, 1, has been achieved in 8 steps starting from readily available, inexpensive ethyl-4-chloroacetoacetate. This synthon serves as one of two main coupling partners in our previously developed Pd-catalyzed alkylative enyne cyclization leading toward the total synthesis of 1α,25-dihydroxyvitamin D 3 and potentially useful analogues.

An efficient route to a key A-ring synthon for 1α,25-dihydroxyvitamin D 3 and its analogs

An efficient and highly stereoselective route to the Roche's A-ring synthon of 1α,25-dihydroxyvitamin D 3 from R-(−)-epichlorohydrin has been developed utilizing double propargylation of R-(−)-epichlorohydrin and palladium(O) catalyzed intramolecular Heck type of reaction of the ω-vinyl-(Z)-iodoalkene as key steps.

An efficient asymmetric synthesis of 1.alpha.,25-(OH)2 vitamin D3 A-ring synthon

Chiral synthesis of the A-ring synthon 3 of 1α,25-dihydroxyvitamin D 3 (1a) based on palladium-catalyzed cyclization of 8-bromo-2,8-nonadienoates is described

Cyanohydrin Alkylation Approach to A Chiral A-Ring Synthon For 1α,25-Dihydroxyvitamin D3

Abstract We report here the synthesis of a chiral A-ring synthon for 1α, 25-dihydroxyvitamin D3 starting from d-mannitol by using the cyanohydrin cyclization methodology.

Pd-Catalyzed Cyclization Approach to Chiral A-Ring Synthon for 1α,2β,25-Trihydroxyvitamin D3

Synthesis of a chiral A-ring synthon for 1α, 2β, 25-trihydroxyvitamin D3 starting from d-mannitol by using palladium-catalyzed cyclization of the (Z)-vinyl iodide is described.

Asymmetric synthesis of a key 1α,25-dihydroxy-vitamin D3 ring a synthon

An efficient and highly stereoselective synthesis of the A-ring synthon 4 of 1,25(OH) 2-vitamin D3 ( 1) is described. The aldehyde 12, which was used for an intramolecular ene reaction to form the main framework 18, was obtained by two different asymmetric approaches starting from olefin 6.

An asymmetric synthesis of a 1α,25-dihydroxyvitamin D3 A-ring synthon

An efficient asymmetric synthesis of the A-ring of 1α,25-dihydroxyvitamin D 3 from α-bromoacrolein is described. The key steps of the synthesis are the Evans type syn-selective asymmetric aldol reaction of bromoacrolein with the boron enolate of 3-chloroacetyl-4(S)-isopropyl oxazolidinone and ring closure by Heck type reaction of a vinyl bromide onto an α,β-unsaturated ester in the exo-mode. Graphic The synthesis of 1 is achieved in high yield by intramolecular Heck reaction of 2 which in turn was prepared from α-bromoacrolein via the Evans aldol 3 .

25-hydroxydihydrotachysterol 2 an innovative synthesis of a key metabolite of dihydrotachysterol 2

A new synthesis of 25-hydroxydihydrotachysterol 2 is described. The hydroxylated side-chain is constructed stereoselectively using a chiral Wittig reagent. The A-ring synthon is introduced utilising the Wittig-Horner method as developed by Lithgoe et al. The preparation of the metabolite is carried out in 18 steps.

An enantioselective synthesis of the A-ring synthon for vitamin D3 metabolites by chemicoenzymatic approach

The A-ring synthon for vitamin D3 metabolites having 1α hydroxyl group is synthesized starting from a chiral monoester 6 enzymatically generated.

A short, enantiospecific synthesis of the 1α-hydroxyvitamin D enyne A-ring synthon

The vitamin D A-ring synthon, the enyne 3b, was synthesized in 5 steps (37% overall yield) from (S)-(+)-carvone ( 5). The key step was the SmI 2-Pd 0 mediated transformation of epoxypropargyl ester 6 to 3b.

ChemInform Abstract: Stereocontrolled Total Synthesis of 1α,25‐Dihydroxyergocalciferol.

AbstractAstereocontrolled total synthesis of the vitamin D2 metabolite (XI), which involves a coupling of the previously described Aring synthon (X) with the appropriately functionalized C‐ Dmoiety (IX), is described.