Re‐investigation of the l‐proline catalyzed double aldol cascade dimerization of succinaldehyde for the synthesis of a key bicyclic enal intermediate, pertinent in the field of stereoselective prostaglandin synthesis, is reported. The yield of this process has been more than doubled, from 14 % to a 29 % isolated yield on a multi‐gram scale (32 % NMR yield), through conducting a detailed study of the reaction solvent, temperature, and concentration, as well as a catalyst screen. The synthetic utility of this enal intermediate has been further demonstrated through the total synthesis of Δ12‐prostaglandin J3, a compound with known anti‐leukemic properties.

Highly chemoselective conjugate reduction of chiral alpha,beta-unsaturated amino ketones has been developed by using triisopropyl phosphite ligated copper hydride complex. The highlights of the method are wide substrate compatibility and exceptional chemoselectivity.

In this review the marine derived decahydroquinoline alkaloid chemistry and biology is described. A proposal is made for the biosynthetic relationships between acyclic and cyclic C-18 amino alcohol natural products.Keywords: amino alcohols, decahydroquinolines, asymmetric synthesis, biosynthesis, total synthesis. Decahydroquinoline (DHQ) alkaloids are unique natural products that can be divided into three distinct sets. The first group (more than 50 members) of these alkaloids are simple 2,5-disubstituted DHQs isolated from dart poison frogs and ants with the parent member being alkaloid cis-195A, also known as pumiliotoxin C [1]. These diverse cis-or trans-fused decahydroquinolines are equipped with various short alkyl and alkenyl side chains. The structurally related but biologically different lepadins 1-8 (Fig. 1) are on the other hand marine alkaloids isolated from three distinct ascidians: Clavelina lepadiformis (found in the North Sea), Didemnum, and Aplidium tabascum (both found in the Great Barrier Reef) [2][3][4][5]. The third group consists of more complex polycyclic alkaloids that besides the DHQ ring system, can contain several other heterocyclic ring systems fused into one molecule. Representative members of this group are gephyrotoxin and Lycopodium alkaloids [6,7]. This review will focus solely on the second group of DHQ alkaloids which, as distinct from the other two groups of DHQ-containing alkaloids, have not been reviewed in full so far [8]. Lepadin alkaloids differ from dendrobatin frog alkaloids in additional oxygenation at position 3, where the substituent may be a hydroxy or acyloxy group, as well as having eight-carbon long side chains of variable oxidation level at position 5 of the DHQ ring. There are three stereochemical groups of lepadins, each derived from distinct tunicate species (Fig. 1). Lepadin F is an exception, being present in both ascidians from the Great Barrier Reef. Lepadins possess some interesting biological activities: lepadins A and B -cytotoxicity against cancer cell lines, lepadins D-F -antiplasmodal and antitrypanosomal activity. Lately, lepadin B together with pictamine was found to block neuronal nicotinic acetylcholine receptors α4β2 and α7. However, the availability of only small quantities of these natural products has precluded further studies on the development into potential leads for nicotinic based therapies [9].

Review: 35 refs.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.