Schmidt Reaction of ω-Azido Valeryl Chlorides Followed by Intermolecular Trapping of the Rearrangement Ions: Synthesis of Assoanine and Related Pyrrolophenanthridine Alkaloids

Synthesis of Amides via the Amination of Aldehydes with Hydroxylamines Promoted by TBAF·3H2O

A metal-free, mild, and efficient method for the synthesis of amides has been developed from the amination of aldehydes with hydroxylamines promoted by TBAF·3H2O in the presence of KOH. Control experiments showed that the nitrone was the intermediate of this amination. By this method, a series of amides, biologically active compounds bebenil and a COX inhibitor were obtained in moderate to good yields.

Divergent Total Syntheses of Lycorine Alkaloids via a Sequential C-H Functionalization Strategy

A Pd-catalyzed one-pot sequential C-H functionalization strategy was utilized to prepare four lycorine alkaloids and one pseudo-lycorine alkaloid from the common intermediate 4. By switching the followed oxidative conditions of air, DMSO/H2O/I2, and DMSO/O2, based on the Pd(PPh3)4/K2CO3/toluene catalytic system, three key intermediates 12a, 12b, and 12c with different substitution patterns could be obtained in a well-controlled manner. As a result, four natural products γ-lycorane, hippadine, anhydrolycorinone, and anhydrolycorine as well as a pseudo-lycorine alkaloid Δ(4a,10b)-6-oxodihydrolycorine were successfully synthesized within 10 steps through this divergent route.

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

An Intramolecular Schmidt Reaction of δ-Azido N-Acylbenzotriazoles

A Lewis acid promoted intramolecular Schmidt reaction of N-acylbenzotriazoles with alkyl azides was designed and realized. The benzotriazole was not only employed as an efficient activator for initiating the Schmidt rearrangement but also used as a powerful terminator for the subsequent nucleophilic trapping of the isocyanate ion and/or N-acyliminium ion from the rearrangement. Thirteen δ-azido N-acylbenzotriazoles were investigated, and the conversion afforded the desired benzotriazole-1-carboxamides and lactams with good to excellent yields.

One pot synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles via tandem C–H olefination/aza-Michael addition

An unprecedented one-pot C–H olefination/aza-Michael addition tandem process has been developed for the synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles and alkenes using a [Cp*RhCl₂]₂/AgOAc/Me₄NOAc catalytic system.