Lactones in the Synthesis of Prostaglandins and Prostaglandin Analogs

In the total stereo-controlled synthesis of natural prostaglandins (PGs) and their structural analogs, a vast class of compounds and drugs, known as the lactones, are encountered in a few key steps to build the final molecule, as: δ-lactones, γ-lactones, and 1,9-, 1,11-, and 1,15-macrolactones. After the synthesis of 1,9-PGF2α and 1,15-PGF2α lactones, many 1,15-lactones of E2, E3, F2, F3, A2, and A3 were found in the marine mollusc Tethys fimbria and the quest for understanding their biological role stimulated the research on their synthesis. Then 1,9-, 1,11-, and 1,15-PG lactones of the drugs were synthesized as an alternative to the corresponding esters, and the first part of the paper describes the methods used for their synthesis. The efficient Corey procedure for the synthesis of prostaglandins uses the key δ-lactone and γ-lactone intermediates with three or four stereocenters on the cyclopentane fragment to link the PG side chains. The paper describes the most used procedures for the synthesis of the milestone δ-Corey-lactones and γ-Corey-lactones, their improvements, and some new promising methods, such as interesting, new stereo-controlled and catalyzed enantioselective reactions, and methods based on the chemical/enzymatic resolution of the compounds in different steps of the sequences. The many uses of δ-lactones not only for the synthesis of γ-lactones, but also for obtaining 9β-halogen-PGs and halogen-substituted cyclopentane intermediates, as synthons for new 9β-PG analogs and future applications, are also discussed.

Diastereoselective Total Synthesis of (+)-Raputindole A: An Iridium- Catalyzed Cyclization Approach

This work describes the total synthesis of Raputindole A <b>(1)</b> through a convergent approach which features: 1) an iridium-catalyzed cyclization to assembly the tricyclic core of the northern part, 2) enzymatic resolution to secure the preparation of enantiomerically pure benzylic alcohol, 3) installation of the butenyl substituent via methallylation of the corresponding benzylic carbocation and coupling of the northern and southern parts via Heck reaction. (+)-Raputindole A <b>(1)</b> was prepared in 10 steps (LLS) and 10% overall yield.

Diastereoselective Total Synthesis of (+)-Raputindole A: An Iridium- Catalyzed Cyclization Approach

This work describes the total synthesis of Raputindole A <b>(1)</b> through a convergent approach which features: 1) an iridium-catalyzed cyclization to assembly the tricyclic core of the northern part, 2) enzymatic resolution to secure the preparation of enantiomerically pure benzylic alcohol, 3) installation of the butenyl substituent via methallylation of the corresponding benzylic carbocation and coupling of the northern and southern parts via Heck reaction. (+)-Raputindole A <b>(1)</b> was prepared in 10 steps (LLS) and 10% overall yield.

Formal enantioselective synthesis of nhatrangin A

A new and straightforward synthesis of the C1–C7 core fragment of nhatrangin A was achieved in 14 steps from achiral 3-hydroxybenzaldehyde, without the need of chiral reagents or enzymatic resolution to introduce the chiral centers.

Stereoselective Synthesis of the A,E-Ring Bicyclic Core of Calyciphylline B-Type Alkaloids

A stereoselective synthesis of the bicyclic unit constituting the A and E rings of calyciphylline B-type alkaloids is disclosed. The propionate ester of (1R)-cyclohex-2-en-1-ol, obtained by enzymatic resolution, is subjected to an Ireland–Claisen rearrangement. Subsequent reduction of the acid, Mitsunobu reaction to introduce a nitrogen functionality, oxidative cleavage to a dialdehyde, and intramolecular aldol and aza-Michael reactions afford the bicyclic subunit.

A facile and regioselective multicomponent synthesis of chiral aryl-1,2-mercaptoamines in water followed by monoamine oxidase (MAO-N) enzymatic resolution

A microwave assisted multicomponent protocol on water allows the regioselective synthesis of chiral aryl-1,2-mercaptoamines. The enzymatic resolution of the racemates leads to enantioenriched products.