Asymmetric synthesis of tetrahydroisoquinolines by enzymatic Pictet-Spengler reaction.

Norcoclaurine synthase (NCS) catalyzes the stereoselective Pictet-Spengler reaction between dopamine and 4-hydroxyphenylacetaldehyde as the first step of benzylisoquinoline alkaloid synthesis in plants. Recent studies suggested that NCS shows relatively relaxed substrate specificity toward aldehydes, and thus, the enzyme can serve as a tool to synthesize unnatural, optically active tetrahydroisoquinolines. In this study, using an N-terminally truncated NCS from Coptis japonica expressed in Escherichia coli, we examined the aldehyde substrate specificity of the enzyme. Herein, we demonstrate the versatility of the enzyme by synthesizing 6,7-dihydroxy-1-phenethyl-1,2,3,4-tetrahydroisoquinoline and 6,7-dihydroxy-1-propyl-1,2,3,4-tetrahydroisoquinoline in molar yields of 86.0 and 99.6% and in enantiomer excess of 95.3 and 98.0%, respectively. The results revealed the enzyme is a promising catalyst that functions to stereoselectively produce various 1-substituted-1,2,3,4-tetrahydroisoquinolines.

Heterogeneous aromatic amination of aryl halides with arylamines in water with PS-PEG resin-supported palladium complexes.

Catalytic aromatic amination is achieved in water under heterogeneous conditions by the use of immobilized palladium complexes coordinated with the amphiphilic polystyrene-poly(ethylene glycol) resin-supported di(tert-butyl)phosphine ligand. Aromatic amination of aryl halides with diphenylamine and N,N-double arylation of anilines with bromobenzene were found to proceed in water with broad substrate tolerance to give the triarylamines in high yield with high recyclability of the polymeric catalyst beads. Very little palladium leached from the polymeric catalyst under the water-based reaction conditions to provide a green and clean (metal-uncontaminated) protocol for the preparation of triarylamines, including the optoelectronically active N,N,N',N'-tetraaryl-1,1'-biphenyl-4,4'-diamines (TPDs).

Clean synthesis of triarylamines: Buchwald-Hartwig reaction in water with amphiphilic resin-supported palladium complexes.

Catalytic aromatic amination was achieved in water under heterogeneous conditions by the use of palladium complexes anchored to the amphiphilic PS-PEG resin with little palladium leaching to provide a green and clean (metal-uncontaminated) protocol for the preparation of triarylamines, including the optoelectronically active N,N,N',N'-tetraaryl-1,1'-biphenyl-4,4'-diamines (TPDs).

Glicentin inhibits internalization of enteric bacteria by cultured INT-407 enterocytes.

Glicentin, the main component of enteroglucagon, has trophic effects on intestinal mucosa. It may also have an inhibitory effect on extraintestinal invasion of enteric bacteria. We have established an in vitro bioassay system for determining the effects of recombinant human glicentin on bacterial internalization by confluent enterocytes. An INT-407 cell line was serum-deprived for 2 days and was then treated on transwell filters for 24 h with a medium containing one of the following: glicentin 100 ng-1 microg/ml, glucagons-like peptide-2 (GLP-2) 1 microg/ml, 10% fetal bovine serum (FCS), or without any growth factors. Pure cultures of Salmonella enteritidis, Escherichia coli, and Enterococcus faecalis were introduced to the upper chambers of the filter units. Following 2 h of incubation the numbers of bacteria in the lower chambers were measured. Pretreatment of enterocytes with glicentin inhibited bacterial internalization compared to untreated or GLP-2 enterocytes. Glicentin was associated with inhibition of enterocyte internalization of enteric bacteria by a mechanism that might be related to the integrity of the enterocyte adhesive junctions and tight junctions and to the production of sIgA. Glicentin seems to have a function as a barrier-sustaining agent that inhibits extraintestinal invasion of enteric bacteria.

A technique using a rectus abdominis muscle flap in the treatment of adult congenital tracheoesophageal fistulas.

The authors successfully treated an adult with congenital tracheoesophageal fistula (TEF) Gross-C type by the addition of an effective pedicled muscle flap. This patient had undergone 2 thoracotomies when he was an infant at another hospital; however, the fistula recurred. After transection and closure of the fistula, a right rectus abdominis muscle flap between the 2 stumps was interposed. The current case followed a favorable postoperative course; neither fistula nor abdominal hernia occurred.