“One-step” synthesis of nonsolvated aluminum hydride

The direct reaction of lithium tetrahydroaluminate with aluminum chloride in an ether— toluene mixture at temperatures ≥90 °? was studied. Under these conditions, nonsolvated aluminum hydride is formed in a yield ≥80%. The product formed represents agglomerates with the highly developed surface and has satisfactory hydrolytic and thermal stability but an increased lithium chloride content (0.25–2.2 wt.%). The decrease in the percentage of this impurity to 0.2 wt.% is achieved by using chloroalanes AlH^b3-n Cl^bn ?xOEt^b2 (n ≤ 1) instead of aluminum chloride along with vigorous stirring and an increase in the synthesis—crystallization temperature to >100 ° ?. The use of compounds based on magnesium tetrahydroaluminate, LiAlH^b4? Mg(AlH^b4)^b2 or LiCl? Mg(AlH^b4)^b2, as modifying agents increases the thermal stability of the hydride and decreases the agglomeration of the crystals.     

Direct synthesis of α-thio aromatic acids from aromatic amino acids

Modified amino acids are useful synthetic components in both chemistry and biology. Here we describe a simple, scalable two-step procedure to generate α-thio aromatic acids from aromatic amino acids with yields of up to 96%. Diazotization and α-lactone mediated bromination efficiently form the α-bromo acid with retention of configuration. Thiol substitution with mild reagents such as sodium hydrosulfide or sodium trithiocarbonate provides the inverted, free α-thio acid. The mildly acidic soft nucleophile can then be utilized in many synthetic applications.     

Hydroalumination of terminal β-acetylene alcohols with lithium aluminum hydride

Hydrogenation of terminal β-acetylene alcohols with lithium aluminum hydride in THF has afforded homoallylic alcohols. Decomposition of the intermediate organoaluminum complex with deuterated water, iodine, or pyridinium dibromide has evidenced about the non-regioselective hydride attack at the triple bond.     

The synthesis of ω-thienylalkane acids from ω-chloroalkane acids

Summary We have worked out a preparative method for the synthesis of -thienylalkane acids by acylation of thiophene with -chloroalkane acid chlorides followed by conversion of the resulting -chloroalkyl(2-thienyl)ketones into the corresponding acids by reaction with sodium malonic ester or potassium cyanide, and reduction of the resulting products with their simultaneous hydrolysis.Here and later we mean -(2-thienyl)alkne acids.We take this opportunity to thank R. Kh. Freidlina, A. A. Beér, and M. A. Besprozvannii for giving us enough -chloroalkane acids.     

Enantiopure synthesis of side chain-modified α-amino acids and 5-cis-alkylprolines

A short, concise synthesis of enantiopure, side chain-modified α-amino acids such as 4-oxo-L-norvaline, 6-oxo-L-homonorleucine, and 5-cis-alkyl prolines is described. Knoevenagel condensation of l-aminocarboxylate-derived β-ketoesters with aldehydes followed by reductive decarboxylation results in unnatural α-amino acids in good yield. A fluorescent amino acid is synthesized using a similar protocol. These studies show that aminocarboxylate-derived β-ketoesters are very useful intermediates and the method employed is both general and practical for the preparation of γ(δ)-oxo α-amino acids and alkylprolines.     

Reduction ofβ-amino acids with lithium aluminum hydrids

Summary Some-amino acids were reduced to the corresponding amino alcohols with the aid of lithium aluminum hydride.Deceased.     

Preparative synthesis of functionally substituted esters of dehydroabietic and 4,4′-biphenyldicarboxylic acids

A preparative synthesis of functionally substituted esters of dehydroabietic and 4,4-biphenylcarboxylic acids by the reaction of chlorides of these acids with alcohols in the presence of pyridine is developed. 4,4-Biphenyldicarbonyl dichloride reacts with hydroperoxides to form peroxy esters and with lithium alcoholates, which allows preparation of the corresponding ethers derived from secondary and tertiary alcohols.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1360–1364.Original Russian Text Copyright © 2004 by Dikusar, Yuvchenko, Kozlov, Olkhovik, Potkin.This revised version was published online in April 2005 with a corrected cover date.     

Progress toward the synthesis of piperazimycin A: exploration of the synthesis of γ-hydroxy and γ-chloropiperazic acids

Employing Hamada’s chemistry with MAOS optimization of several steps, an expedient route to key (3S,5S)- and (3R,5R)-γ-hydroxy and (3R,5S)-γ-chloropiperazic acids, was developed en route to a total synthesis of piperazimycin A.     

Reactions of β-keto sulfones with t-butyl aluminum compounds: Reinvestigation of tri-t-butyl aluminum synthesis

t-Butyl derivatives play a significant role in the organometallic chemistry of group 13 metals. It was shown on the basis of reactions of t-Bu₃Al·OEt₂ with [p-RC₆H₄S(O)₂C(H)₂C(Ph) = O] (where R = CH₃, Cl) β-keto sulfones that the structure of the reaction products depends on the purity of the aluminum compound used. In the reactions, in addition to the expected complexes [p-RC₆H₄S(O₂)C(H) = C (Ph)-OAl(t-Bu)₂] [where R = CH₃ ( 2 ); R = Cl ( 4 )] possessing β-keto sulfone ligands, complexes with β-hydroxy sulfone ligands [p-RC₆H₄S(O₂)C(H)₂-C (Ph)-OAl(t-Bu)₂] [where R = CH₃ ( 1 ); R = Cl ( 3 )] were formed. Compounds 1 and 3 were the result of the hydroalumination reaction of the β-keto sulfone ligands with t-Bu₂AlH, which is an impurity of t-Bu₃Al. These compounds are obtained, for the first time, as intermediate products in the hydrogenation reaction of β-keto sulfones. In this work, during t-Bu₃Al·OEt₂ production t-Bu₂AlH·OEt₂ formed as a by-product. Re-examination of reaction conditions of AlCl₃ with t-BuMgCl resulted in a control of the t-Bu₂AlH·OEt₂ by-product content in t-Bu₃Al·OEt₂.     

Facile synthesis and structural characterization of μ4-oxo tetrazinc clusters of beyerenoic and kaurenoic acids

The naturally occurring diterpenoids beyerenoic (1) and kaurenoic acids (2) extracted from Perymenium buphthalmoides DC., were treated with NaOH and reacted with ZnCl₂ to afford two μ₄-Oxo tetrazinc clusters (μ₄-oxo)-hexakis(μ₂-beyerenate)-tetra-zinc(II) (5) and (μ₄-oxo)-hexakis(μ₂-kaurenate)-tetra-zinc(II) (6). Both species were unequivocally characterized and their structures in the solid state determined by single crystal X-ray diffraction techniques.     

A new general, practical and enantioselective synthesis of α-amino acids

In recent years, considerable efforts have been expended to the development ofenantioselective synthesis of α-amino acids and the use of α-amino acids as chiralbuilding blocks for the synthesis of complex molecules. Numerous unnatural aminoacids which are often the characteristic units of biologically active peptides, have alsobeen discovered. Herein we describe a convenient and general access to natural andunnatural α-amino acids which are based on the use of the chiral building blocks,(S)-1a-e and (R)-1a-e from kinetic resolution of α-furfuryl amines (Scheme 1).     

Ruthenium-catalyzed selective synthesis of monoalkylated barbituric acids through “borrowing hydrogen” methodology

An environmentally benign alkylation of barbituric acids via “borrowing hydrogen” process with ruthenium catalysis has been established. The corresponding 5-(alkyl)barubituric acids were obtained in good to excellent yields with low catalyst loading. Various substrates including aliphatic alcohols were tolerated in the present catalytic system. A novel method for construction of barbituric acid-fused benzopyrane derivatives was also demonstrated.     

Stereo- and regio-selective one-pot synthesis of triazole-based unnatural amino acids and β-amino triazoles

Synthesis of triazole based unnatural amino acids and β-amino triazoles has been described via a stereo and regioselective one-pot multi-component reaction of sulfamidates, sodium azide, and alkynes under MW conditions. The developed method is applicable to a broad substrate scope and has significant potential for the synthesis of unnatural amino acids with a triazole side chain.     

Red yeast catalyzed animation of olefinic bonds and synthesis of optically pure S-amino acids

By using red yeast (Rhodotorula rubra AS 2.166) resting cells which possess the phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity as biocataiyst, enantiomerically pure S-3-(2-chloro-phenyl) alanine (2a) and S-3-(3-hydroxyphenyl) alanine (2d) have been synthesized from the corresponding 3-aryl substituted acrylic acid (1a and 1d) and ammonia.