Synthesis of 3-Carbonyl Trisubstituted Furans via Pd-Catalyzed Aerobic Cycloisomerization Reaction: Development and Mechanistic Studies.

Herein, we report the synthesis of 3-carbonyl-trisubstituted furans via Pd-catalyzed oxidative cycloisomerization reactions of 2-alkenyl-1,3-dicarbonyl scaffolds, using molecular oxygen as the sole oxidant to regenerate active palladium catalytic species, featuring good functional tolerance and mild reaction conditions. Deep investigation of intermediates and transition states of the reaction mechanism were conducted via experimental and DFT studies, providing a detailed mechanistical profile. The new developed methodology presents a greener alternative to Wacker-type cycloisomerizations and avoids the use of stoichiometric amounts of oxidants and strong acid additives.

Six-Step Syntheses of (-)-1-Deoxyaltronojirimycin and (+)-1-Deoxymannonojirimycin from N-Z-O-TBDPS-l-serinal.

Highly stereoselective six-step syntheses of (-)-1-deoxyaltronojirimycin (altro-DNJ) and (+)-1-deoxymannojirimycin (manno-DNJ) from N-Cbz-O-TBDPS-l-serinal are described. Key transformations involve a two-step preparation of a functionalized dihydropyridin-3-one as a common intermediate followed by Luche reduction and dihydroxylation (for altro-DNJ). The same sequence employing an epoxidation/epoxide opening in place of dihydroxylation furnishes manno-DNJ.

Three-step synthesis of (±)-preussin from decanal.

A straightforward and stereoselective synthesis of the alkaloid preussin is described starting from decanal and diethyl 3-diazo-2-oxopropylphosphonate. The key steps are an aza-Michael reaction from an α,ß-unsaturated diazoketone followed by a highly stereoselective Cu-catalyzed ylide formation and then a [1,2]-Stevens rearrangement. This strategy is feasible for extension to preussin analogues, demonstrating its utility for the rapid construction of all-cis-substituted pyrrolidines.

Synthesis of alkaloids: recent advances in the synthesis of phenanthroindolizidine alkaloids.

Phenanthroindolizidine alkaloids are a well-known class of compounds due to their interesting biological activities, especially anticancer ones. Represented by more than 60 substances, they are mainly isolated from plants of the Moraceae and Asclepiadaceae families. In the last 30 years, a great effort has been made aiming the synthesis of these compounds and analogues to be applied in medicinal chemistry.

Preparation of Z-α,ß-unsaturated diazoketones from aldehydes. Application in the construction of substituted dihydropyridin-3-ones.

The stereoselective preparation of α,ß-unsaturated diazoketones with Z geometry is described from aldehydes and a new olefination reagent. When prepared from amino aldehydes, these diazoketones could be converted to substituted dihydropyridin-3-ones in just one step, after an intramolecular N-H insertion reaction. The straightforward synthesis of a natural trihydroxylated piperidine demonstrates the utility of these unsaturated diazoketones for the rapid construction of piperidines.

Bioconversion of iodoacetophenones by marine fungi.

Nine marine fungi (Aspergillus sclerotiorum CBMAI 849, Aspergillus sydowii Ce19, Beauveria felina CBMAI 738, Mucor racemosus CBMAI 847, Penicillium citrinum CBMAI 1186, Penicillium miczynskii Ce16, P. miczynskii Gc5, Penicillium oxalicum CBMAI 1185, and Trichoderma sp. Gc1) catalyzed the asymmetric bioconversion of iodoacetophenones 1-3 to corresponding iodophenylethanols 6-8. All the marine fungi produced exclusively (S)-ortho-iodophenylethanol 6 and (S)-meta-iodophenylethanol 7 in accordance to the Prelog rule. B. felina CBMAI 738, P. miczynskii Gc5, P. oxalicum CBMAI 1185, and Trichoderma sp. Gc1 produced (R)-para-iodophenylethanol 8 as product anti-Prelog. The bioconversion of para-iodoacetophenone 3 with whole cells of P. oxalicum CBMAI 1185 showed competitive reduction-oxidation reactions.