Synthesis of lactams by radical substitution reaction of alpha,beta-unsaturated acyl radicals at amine nitrogen

[reaction: see text] Substitution at nitrogen by alpha,beta-unsaturated acyl radicals took place accompanied by elimination of an alpha-phenethyl radical. This reaction led to the development of a new carbonylative annulation method for five- to seven-membered ring lactams.     

Tandem gold(I)-catalyzed cyclization/electrophilic cyclopropanation of vinyl allenes

We have developed an expedient method for the synthesis of polycyclic compounds from propargyl acetates or vinyl allenes involving up to three Au(I)-catalyzed elemental steps: 3,3-rearrangement, metalla-Nazarov reaction, and electrophilic cyclopropanation. The reaction proceeds under very mild conditions and in short times. The mechanism has been studied by DFT computations.     

Ru-catalyzed intermolecular [3+2+1] cycloaddition of alpha,beta-unsaturated ketones with silylacetylenes and carbon monoxide leading to alpha-pyrones

Ruthenium catalyzes a carbonylative [3+2+1] cycloaddition, using silylacetylenes, alpha,beta-unsaturated ketones, and CO as the starting materials, providing the new method for the synthesis of tetrasubstituted alpha-pyrones. In this reaction, the carbonyl group and alpha-carbon of vinyl ketones are incorporated as a three-atom assembling unit. [reaction: see text].     

Ruthenium hydride-catalyzed addition of aldehydes to dienes leading to beta,gamma-unsaturated ketones

An efficient cross-addition reaction of dienes with aldehydes was developed by using RuHCl(CO)(PPh3)3 as a catalyst to give a wide variety of beta,gamma-unsaturated ketones, where a pi-allylruthenium species, derived from hydroruthenation of diene, may be involved as a key intermediate.     

1,2-Bis(o-aminophenoxy)ethane-N,N, N′, N′-tetra-acetic acid derivatives on complexation with lanthanoid metal ions. Correlation between size of trapping hole and metal ion

Complexation of lanthanoid metal ions with 1,2-bis(o-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid and its two derivatives, in which the distance between the chelating functions is changed, has been studied by potentiometric pH titration. There are two complexation modes depending on the size of the metal ion. Structural flexibility of the chelator accounts for the change in the complexation mode.     

Identification of (6R)‐5,6,7,8‐Tetrahydro‐D‐monapterin (=(6R)‐2‐Amino‐5,6,7,8‐tetrahydro‐6‐[(1R,2R)‐1,2,3 ‐trihydroxypropyl]pteridin‐4(3H)‐one) as the Native Pteridine in Tetrahymena pyriformis

The structure of the native pteridine in Tetrahymena pyriformis was determined as (6R)‐5,6,7,8‐tetrahydro‐D ‐monapterin (=(6R)‐2‐amino‐5,6,7,8‐tetrahydro‐6‐[(1R,2R)‐1,2,3‐trihydroxypropyl]pteridin‐4(3H)‐one; 4 ). First, the configuration of the 1,2,3‐trihydroxypropyl side chain was confirmed as D ‐threo by the fluorescence‐detected circular dichroism (FDCD) spectrum of its aromatic pterin derivative 2 obtained by I₂ oxidation (Fig. 1). The configuration at the 6‐position of 4 was determined as (R) by comparison of its hexaacetyl derivative 6 with authentic (6R)‐ and (6S)‐hexaacetyl‐5,6,7,8‐tetrahydro‐D ‐monapterins 6 and 7 , respectively, in the HPLC, LC/MS, and LC‐MS/MS (Figs. 3 – 6). (6R)‐5,6,7,8‐Tetrahydro‐D ‐monapterin ( 4 ) is a newly discovered natural tetrahydropterin.     

Synthesis of polymers containing conjugated dienyl end-groups by means of anionic living polymerization

In order to synthesize end-functionalized polymers with conjugated dienyl groups, living polymeric anions of polystyrene and polyisoprene were allowed to react with 5-bromo-1,3-pentadiene, 1, and 7-bromo-1,3-heptadiene, 2. The reaction of polystyryl anion and/or polyisoprenyl anion with 1 gave polymers whose end-functionalities were 65–80% regardless of the reaction conditions. On the other hand, almost quantitative functionalization was achieved when a large excess amount of 2 was used as a terminator. When 1,1-diphenylalkyl anion and enolate anion derived from t-butyl methacrylate were used, the degree of end-functionality were 70–80% at best. The resulting end-functionalized polymers were characterized by size exclusion chromatography (SEC), ¹H and ¹³C-NMR and thin layer chromatography coupled with a flame ionization detector (TLC-FID). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3464–3472, 1999     

Coupling‐Reagent‐Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids

A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl‐glycyl‐glycine, present in IMREG‐1, also.