Palladium on carbon-diethylamine-mediated hydrodeoxygenation of phenol derivatives under mild conditions

Total Synthesis of 19-Nordigitoxigenin, An Antiaroside Y Aglycon

The first total synthesis of 19-nordigitoxigenin, an aglycon of antiroside Y, has been achieved. The key steps of our synthesis are (i) construction of the 19-norsteroid ring system via a Mizoroki-Heck reaction between a bromoanisole corresponding to the A-ring and cyclic alkene incorporating the CD-rings, followed by a Friedel-Crafts-type cyclodehydration, and (ii) incorporation of the butenolide moiety at C17 via a silyl-tethered radical cyclization and subsequent ozone oxidation.

Synthesis of 13C/19F/2H labeled indoles for use as tryptophan precursors for protein NMR spectroscopy

Synthesis of indoles labeled with 13C-1H and 13C-19F spin pairs is described. All syntheses utilize inexpensive carbon-13C dioxide as the 13C isotope source. Ruthenium-mediated ring-closing metathesis is the key step in construction of the 13C containing indole carbocycle. Fluorine is introduced via electrophilic fluorination at the 7-position and via palladium-mediated cross-coupling at the 4-position. Indole and fluoroindoles are viable tryptophan precursors for in vivo protein expression. We show that they are viable also in in vitro protein synthesis using standard E. coli S30 extracts. Incorporation of the synthesized 13C-1H and 13C-19F spin pair labeled tryptophans into proteins enables high-resolution and high-sensitivity nuclear magnetic resonance (NMR) spectroscopy.

Silanediol-Catalyzed Chromenone Functionalization

Promising levels of enantiocontrol are observed in the silanediol-catalyzed addition of silyl ketene acetals to benzopyrylium triflates. This rare example of enantioselective, intermolecular chromenone functionalization with carbonyl-containing nucleophiles has potential applications in the synthesis of bioactive chromanones and tetrahydroxanthones.

Metal catalyzed defunctionalization reactions

The chronological development of metal assisted defunctionalization reactions is discussed from the stoichiometric to the catalytic stage with their application in synthetic organic chemistry.

Ethers as hydrogen sources in BF3·OEt2 promoted reduction of diphenylmethyl alcohols, ethers and esters to hydrocarbons

A novel ether/BF₃ reductive system is effective for the reduction of diphenylmethanols and their ether and ester derivatives into hydrocarbons.

Synthesis and biological activity of optically active phenylbutenoid dimers

The total synthesis of optically active phenylbutenoid dimers 1, 3, and ent-3 is described. The key step to access optically active cyclohexene rings was achieved by Diels-Alder reaction of chiral acryloyloxazolinone 9 and phenylbetadiene 10.