A practical synthesis of L-ribose

L-Ribose was synthesized by a simple four-step method with overall yield of 76.3% from a protected L-arabinose derivative, which is a compatible intermediate for the synthesis of L-deoxyribose. The key step of this strategy is the Swern oxidation and subsequent stereoselective reduction accompanied by inversion of the 2-hydroxy group of protected L-arabinose.     

Confirmation of the structure of a glucono-1,4-lactone derivative obtained from silylation of glucono-1,5-lactone

Silylation reactions of glucono-1,5-lactone can give the persilylated glucono-1,5-lactone or the persilylated 1,4-lactone depending on the reaction conditions employed. The structure of 2,3,5,6-tetra-O-(tert-butyldimethylsilyl)-d-glucono-1,4-lactone, obtained in 84% yield from the reaction of glucono-1,5-lactone with TBSOTf and lutidine in dichloromethane, has been confirmed by X-ray crystallography. Formation of the glucono-1,5-lactone and manno-1,5-lactone derivatives and other possible products has also been ruled out by synthesis of possible exo-glycal derivatives of these lactones using the Ramberg–Bäcklund rearrangement of the corresponding sulfones.     

An efficient synthesis of l-allono-1,4-lactone from 2,3:5,6-di-O-isopropylidene-d-mannono-1,4-lactone

We reported herein an efficient synthesis of l-allono-1,4-lactone from 2,3:5,6-di-O-isopropylidene-d-mannono-1,4-lactone in five steps. The key feature of this method involved a one-pot, ‘double inversion’ procedure at the stereocenters of C-4 and C-5 of d-mannono-1,4-lactone to afford the target molecule.     

Pyrazolones and quinoxalines from 4-phenyl-2,3-dioxobutyro-1,4-lactone

4-Phenyl-2,3-dioxobutyro-1,4-lactone ( 1 ) gave with phenylhydrazine and ils p-Cl, p-Br, p-I and p-NO₂ derivatives, bishydrazones which were eyclized to 1-aryl-3-(α-hydroxybenzyl)-4,5-dione-4-arylhydrazones. With o-phenylene diamine, compound 1 gave either a Schiff base or a substituted quinoxaline, depending upon the ratio of the reactants.     

Novel synthesis of 2,3-diarylbuta-1,3-dienes from 1,4-dimethoxybutyne-2

It was found that 2,3-diarylbuta-1,3-dienes were readily obtained in good to excellent yields through the S_N-2′ type substitution of 1,4-dimethoxybutyne-2 with aryl Grignard reagents in the presence of a copper(I) salt.     

Novel solid-state synthesis of dimeric 4-aryl-1,4-dihydropyridines

On irradiation in the solid state the 4-aryl-1,4-dihydroypridines 1 undergo [2+2] cycloadditon to centrosymmetric head-to-tail dimers 3 and 4a . The almost exclusive formation of the cage dimers 3 via the C₂-symmetric syn-dimers 2 takes place in nearly quantitative yields, in contrast with the cycloaddition reaction of the anti-dimer 4a , which is accompanied by photooxidation to pyridine 5a .     

Saccharinic acid lactone from Astragalus Lusitanicus lam. (−)-2-c-methyl-d-erythrono-1,4-lactone

(?)-2-C-methyl-D-erythrono-1,4-lactone has been isolated from $\text{A. lusitanicus}$, its structure being established by spectroscopic methods and synthesis. This is the first report of a natural saccharinic acid lactone.     

Stereoselective synthesis of γ-lactone fused cyclopentanoids

The stereoselective synthesis of γ-lactone fused cyclopentanoids applying chemoenzymatic methods is described. rac-2-Hydroxymethyl-1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-ene and rac-2-hydroxymethyl-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene were successfully resolved by Candida rugosa lipase (CRL), to afford enantiomerically enriched products with an ee of 94 and 97%, respectively. The enantiomerically enriched acetates were then subjected to ruthenium and/or cerium catalyzed oxidation to afford α-diketones and subsequent alkaline H₂O₂ mediated oxidative cleavage reaction of α-diketones, followed by CH₂N₂ esterification, gave enantiomerically enriched γ-lactone fused cyclopentanoids with known absolute configurations.     

Novel synthesis modes and properties of [1,4]benzodioxinopyridazines

A simple synthesis involving fusion of catechol and derivatives with 3,4,5-trichloropyridazine has furnished 4-chloro[1,4]benzodioxino[2,3-c]pyridazines 5 for the first time. This new method complements the previously reported base promoted procedure for preparing 4-chloro[1,4]benzodioxino-[2,3-d]pyridazines 3 . Employing both methods, 4-(trifluoromethyl)catechol was converted to the four regio isomers 3b,c and 5c,d . Structure assignment of these four was aided by the remarkably consistent influence of the pyridazine 4-chlorine substituent and diazo-linkage in inducing ¹H nmr downfield shifts of their nearest neighbor phenyl ring protons. Finally, contrary to what might be expected from previously reported results, reaction of methoxide with either 3 or 5 , gave chlorine substitution with formation of methoxybenzodioxinopyridazines 6 and 7 respectively. However, these reactions both give what appears to be an unprecedented rearrangement, with conversion of [2,3-c]-pyridazine to [2,3-d]pyridazine, and vice versa.     

The first synthesis of N-acetylneuraminic acid 1,7-lactone

N-Acetylneuraminic acid is transformed into its until now unavailable and rather unwieldy 1,7-lactone, via the manageable 2-benzyloxycarbonyl N-acetylneuraminic acid 1,7-lactone which generates the free lactone in quantitative yield by hydrogenolysis.     

Novel synthesis of imidazo[4,5-e][1,4]diazepines

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1140–1141, August, 1990.     

Practical and concise synthesis of 2-oxo-3,4,5,6-tetraethoxyazepane from D-glucono-1,5-lactone

2-Oxo-3R,4S,5S,6S-tetraethoxyazepane was conveniently synthesized from D-glucono-1, 5-1actone with a yield of 10% overall. The key step of synthetic route-reductive 1,6-cyclization was completed efficiently by using Ph3P to give the expected lactam.     

A heterogeneous Pd-Bi/C catalyst in the synthesis of L-lyxose and L-ribose from naturally occurring D-sugars

A critical step in the synthesis of the rare sugars, L-lyxose and L-ribose, from the corresponding D-sugars is the oxidation to the lactone. Instead of conventional oxidizing agents like bromine or pyridinium dichromate, it was found that a heterogeneous catalyst, Pd-Bi/C, could be used for the direct oxidation with molecular oxygen. The composition of the catalyst was optimized and the best results were obtained with 5 : 1 atomic ratio of Pd : Bi. The overall yields of the five-step procedure to L-ribose and L-lyxose were 47% and 50%, respectively. The synthetic procedure is advantageous from the viewpoint of overall yield, reduced number of steps, and mild reaction conditions. Furthermore, the heterogeneous oxidation catalyst can be easily separated from the reaction mixture and reused with no loss of activity.