Asymmetric synthesis of densely functionalized medium-ring carbocycles and lactones through modular assembly and ring-closing metathesis of sulfoximine-substituted trienes and dienynes.

An asymmetric synthesis of densely functionalized 7-11-membered carbocycles and 9-11-membered lactones has been developed. Its key steps are a modular assembly of sulfoximine-substituted C- and O-tethered trienes and C-tethered dienynes and their Ru-catalyzed ring-closing diene and enyne metathesis (RCDEM and RCEYM). The synthesis of the C-tethered trienes and dienynes includes the following steps: 1) hydroxyalkylation of enantiomerically pure titanated allylic sulfoximines with unsaturated aldehydes, 2) α-lithiation of alkenylsulfoximines, 3) alkylation, hydroxy-alkylation, formylation, and acylation of α-lithioalkenylsulfoximines, and 4) addition of Grignard reagents to α-formyl(acyl)alkenylsulfoximines.

Asymmetric modular synthesis of highly functionalized medium-sized carbocycles and lactones via ring-closing metathesis of sulfoximine-substituted trienes.

A modular asymmetric synthesis of medium-sized carbocycles and lactones has been developed that affords highly substituted 7-, 9-, and 11-membered rings. The key steps are (1) the highly diastereoselective synthesis of sulfoximine-substituted homoallylic alcohols from allylic sulfoximines and unsaturated as well as saturated aldehydes, (2) an E-stereoselective alkylation and hydroxyalkylation of sulfoximine-substituted alkenyllithium derivatives, (3) the esterification of sulfoximine-substituted homoallylic alcohols, and (4) the ring-closing metathesis reaction of sulfoximine-substituted trienes with the ruthenium catalyst 8. Two examples for the further synthetic elaboration of the sulfoximine-substituted carbocycles are provided.

Fully stereocontrolled total syntheses of the prostacyclin analogues 16S-iloprost and 16S-3-oxa-iloprost by a common route, using alkenylcopper-azoalkene conjugate addition, asymmetric olefination, and allylic alkylation.

In this article we describe fully stereocontrolled total syntheses of 16S-iloprost (16S-2), the most active component of the drugs Ilomedin and Ventavis, and of 16S-3-oxa-iloprost (16S-3), a close analogue of 16S-2 having the potential for a high oral activity, by a new and common route. The key steps of this route are (1) the establishment of the complete C13-C20 omega side chain of the target molecules through a stereoselective conjugate addition of the alkenylcopper derivative 9 to the bicyclic C6-C12 azoalkene 10 with formation of hydrazone 8, (2) the diastereoselective olefination of ketone 7 with the chiral phosphoryl acetate 39, and (3) the regio- and stereoselective alkylation of the allylic acetate 43 with cuprate 42. These measures allowed the 5E,15S,16S-stereoselective synthesis of 16S-2 and 16S-3, a goal which had previously not been achieved.

Asymmetric synthesis of the highly potent anti-metastatic prostacyclin analogue cicaprost and its isomer isocicaprost.

An asymmetric synthesis of the anti-metastatic prostacyclin analogue cicaprost and a formal one of its isomer isocicaprost by a new route are described. A key step of these syntheses is the coupling of a chiral bicyclic C6-C14 ethynyl building block with a chiral C15-C21 omega-side chain amide building block with formation of the C14-C15 bond of the target molecules. A highly stereoselective reduction of the thereby obtained C6-C21 intermediate carrying a carbonyl group at C15 of the side chain was accomplished by the chiral oxazaborolidine method.