Keteniminium Salts: Reactivity and Propensity toward Electrocyclization Reactions.

A predictive computational study was conducted in order to assess the efficiency of electrocyclization reactions of keteniminium salts, in an effort to form a variety of heterocyclic systems, namely, 3-amino(benzo)thiophenes, 3-amino(benzo)furans, 3-aminopyrroles, as well as 3-aminoindoles. A density functional theory (DFT) approach was utilized and the effect of heteroatoms (NMe, O, S) was thoroughly investigated by means of population analysis, QTAIM, NICS, ACID, and local reactivity descriptors (Parr and Fukui functions). The electrocyclization of enamines leading to 3-aminopyrroles was shown to be both kinetically and thermodynamically most favorable. Moreover, the pericyclic nature of the electrocyclizations was confirmed using FMO, QTAIM, NICS, and ACID methods. Additionally, substituent effects were investigated in order to give further insight on the reactivity of heteroatom containing keteniminium systems toward electrocyclization reactions. Finally, computational predictions were experimentally confirmed for a selection of keteniminium systems.

Total Synthesis of Putative 11-epi-Lyngbouilloside Aglycon.

We report here the total synthesis of 11-epi-lyngbouilloside aglycon. Our strategy features a Boeckman-type esterification followed by a RCM to form the 14-membered ring macrolactone and a late-stage side chain introduction via a Wittig olefination. Overall, the final product was obtained in 20 steps and 2% overall yield starting from commercially available 3-methyl-but-3-enol. Most importantly, the strategy employed is versatile enough to eventually allow us to complete the synthesis of the natural product and irrevocably confirm its structure.

Non-enzymatic acylative kinetic resolution of primary allylic amines.

A non-enzymatic acetyl transfer-based kinetic resolution of primary allylic amines is reported. The process involves the use of (1S,2S)- in conjunction with a supported ammonium salt and affords the corresponding enantio-enriched N-acetylated allylic amines with unprecedented levels of selectivity (s-factors up to 34).

Lyngbouilloside and related macrolides from marine cyanobacteria.

Lyngbouilloside and the related macrolides lyngbyaloside, lyngbyaloside B and lyngbyaloside C have attracted a lot of attention over the past decade due to their intriguing architecture, their natural scarcity and their potential biological activities. This review aims to showcase the various strategies that have been used to access these natural products.

Kinetic resolution of propargylamines via a highly enantioselective non-enzymatic N-acylation process.

The non-enzymatic kinetic resolution of diversely substituted primary propargylic amines is reported featuring a highly selective acetyl transfer using (1S,2S)- in conjunction with Aliquat(TM) 336, affording the corresponding enantio-enriched N-acetylated propargylic amines with unprecedented levels of selectivity (s-factors of up to 193 at 50% conversion).

Stereoselective synthesis of the C1-C11 and C12-C34 fragments of mycalolide A.

A convergent synthesis of the C1-C11 and C12-C34 fragments of mycalolide A is described. Synthetic highlights include a highly E-selective cross-metathesis between a vinyl-functionalized bis-oxazole unit and a polypropionate side chain to introduce the C19-C20 double bond and an enzymatic desymmetrization of a meso-diol in addition to five stereoselective allylations/crotylations to control the 11 stereogenic centers present in the natural product.