Ring expansion of functionalized octahydroindoles to enantiopure cis-decahydroquinolines

A new synthetic entry to enantiopure cis-decahydroquinolines is reported. Endo and exo derivatives of cis-1-benzyl-2-(hydroxymethyl)octahydroindol-6-one ethylene acetal undergo ring enlargement upon treatment with TFAA and then Et3N (thermodynamic conditions) to give enantiopure 1-benzyl-3-hydroxydecahydroquinolin-7-one derivatives in 77 and 82% yield, respectively. For 2-(1-hydroxyethyl) analogues, the best synthetic result is obtained from the (2S,1'R) endo isomer, which under kinetic reaction conditions (MsCl, THF, -20 degrees C, then AgOAc at rt ) gives the expanded product in 54% yield.     

Cobalt-Catalyzed 1,4-Aryl Migration/Desulfonylation Cascade: Synthesis of α-Aryl Amides

A cobalt-catalyzed 1,4-aryl migration/disulfonylation cascade applied to α-bromo N-sulfonyl amides was developed. The reaction was highly chemoselective, allowing the preparation of α-aryl amides possessing a variety of functional groups. The method was used as the key step to synthesize an alkaloid, (±)-deoxyeseroline. Mechanistic investigations suggest a radical process.     

Assembly of the Entire Carbon Backbone of a Stereoisomer of the Antitumor Marine Natural Product Hemicalide

A strategy for the assembly of the entire carbon backbone of a stereoisomer of the antitumor marine natural product hemicalide has been investigated. The devised convergent approach relies on Horner–Wadsworth–Emmons and Julia–Kocienski olefination reactions for the construction of the C6=C7 and C34=C35 double bonds, respectively, an aldol reaction to create the C27−C28 bond, and a Suzuki–Miyaura cross-coupling as the endgame to form the C15−C16 bond.     

Solid phase synthesis of amides by the Beckmann rearrangement of ketoxime carbonates

In the presence of trifluoroacetic acid, ketoxime benzyl carbonates undergo a Beckmann rearrangement to the corresponding amides. This reaction was translated to a solid support by immobilizing oximes in the form of mixed carbonates derived from hydroxymethylpolystyrene in order to produce a diversity of amides with high efficiency.     

Photoreductive cyclization of δ,ϵ-unsaturated ketones

δ,?-unsaturated ketones are efficiently photoreduced in HMPA or tertiary amines. Cyclization to cyclopentanols is the only observed reaction.     

Rhodium‐Catalyzed Cyclization of O,ω‐Unsaturated Alkoxyamines: Formation of Oxygen‐Containing Heterocycles

O,ω‐Unsaturated N‐tosyl alkoxyamines undergo unexpected Rh^III‐catalyzed intramolecular cyclization by oxyamination to produce oxygen‐containing heterocycles. Mechanistic studies show that an aziridine intermediate seems to be responsible for the formation of the heterocycles, possibly via a Rh^V species.     

Synthesis of the c14-c25 subunit of bafilomycin A1

The enantioselective synthesis of the C14-C25 subunit of bafilomycin A1 was realized in a convergent route. The sequence involves two dynamic kinetic resolution steps of 2-alkyl 1,3-diketones that use optically active ruthenium complexes, an anti-selective reduction of a beta-hydroxyketone to control the C23 stereogenic center, and an aldol-type reaction under Evans' conditions, which sets the C17 and C18 stereogenic centers.     

Stereoselective synthesis of the C1-C13 fragment of (+)-discodermolide using asymmetric allyltitanations

[reaction: see text] The synthesis of the C1-C13 fragment of (+)-discodermolide has been achieved. The configurations of the stereogenic centers have been controlled by enantioselective allyl- and crotyltitanations of aldehydes, and the Z configuration of the olefin at C8-C9 was controlled by a ring-closing metathesis.