Stereospecific substitution of enantiomerically pure 1-(2-pyridinyl)ethyl methanesulfonate with beta-dicarbony compounds

The alkylation of the sodium salt of the malonic acid diester with (R)-1-(2-pyridinyl)ethyl methanesulfonate (2) gave the dimethyl (R)-[1-(2-pyridinyl)ethyl]malonate (3a), stereospecifically. The alkylation reaction of methyl acetoacetate gave the methyl (2'S,2R/2S)-3-oxo-2-[1-(2-pyridinyl)ethyl]butanoate (3d) along with the methyl (S)-3-[1-(2-pyridinyl)ethoxy]-2-butenoate (4d). The acid hydrolysis and decarboxylation of 3d under acidic conditions gave (R)-4-(2-pyridinyl)pentan-2-one (6), and the alkylation of methyl (R)-[1-(2-pyridinyl)ethyl]acetoacetate with benzyl bromide gave a mixture of C-benzylated and O-benzylated products 7 and 8.     

Synthesis of 2,2a,4,5-tetraazabenz[cd] azulene derivatives

3-Methyl-1,8-dihydrocycloheptapyrazol-8-one hydrazone ( 5 ) reacted with triethyl ortho-formate, orthoacetate and orthopropionate to afford 2,2a,4,5-tetraazabenz[cd]azulene derivatives ( 7a-c ). 3-Methyl- ( 7b ) and 3-phenyl-substituted compounds ( 7d ) were also obtained by the reactions of 5 with acetyl and benzoyl chlorides, respectively.     

Electrophilic aromatic substitution by pummerer reaction of α-sulfinylacetate

Treatment of a mixture of aromatic compound and ethyl α-(methylsulfinyl)acetate (5) with p-toluenesulfonic acid under continuous removal of separated water brought about an intermolecular aromatic substitution to give ethyl α-(methylthio)arylacetate (6). Similar treatment of acylmethyl phenethyl sulfoxide (8) led to cyclization into 1-acylisothiochroman (9).     

Formal total synthesis of (±)-magellanine

Formal total synthesis of magellanine is described. Key features in the synthesis were stereoselective Ireland-Claisen rearrangement and intramolecular Pauson-Khand reaction of exo-cyclic enynes.     

Radiation-Induced Cross-Linking of Polyethylene in the Presence of Various Acetylenic Compounds

A study was made on the radiation-induced cross-linking reaction of polyethylene by exposing film samples to [ddot]Co γ-rays in vacuum or in the presence of various acetylenic compounds such as acetylene, its C₃ to C₅ higher derivatives, and their mixture with tetrafluoroethylene (TFE). The samples (0.2 mm thick) were found to decrease in weight when irradiated in vacuum, but to increase in the presence of the additives. The IR spectrum measurements of the resultant showed that the trans-vinylene unsaturation increased by the irradiation, especially in the presence of the C₃ to C₅ derivatives, and terminal vinyl increased markedly in acetylene. However, the formation of these unsaturations were depressed when the film was irradiated in the mixed gas with TFE. The rate of the cross-linking reaction was accelerated by the addition of acetylene-TFE, acetylene, trifluoromethyl-acetylene, perfluorobutyne-2, perfluorobutyne-2-TFE, and methylacetylene-TFE [G(cross-linking) = 4.4-1.2]. It was reduced with methylacetylene, butyne-1, butyne-1-TFE, pentyne-1, pentyne-1-TFE, pentyne-2, pentyne-2-TFE, [G(cross-linking) = 0.6-0.1]. On the basis of these experimental results a chain reaction scheme of the cross-linking is proposed, and it is discussed on the basis of the activation energy of the elementary reactions.     

Novel Synthesis and Structure of Phosphanyl Sugar Derivatives 1

Abstract

Some phosphanyl sugar derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen, were synthesized from 2- and 3-phospholenes as starting materials. Catalytic cis-dihydroxylation of 2-phospholene or 3-phospholene 1-oxide derivatives with osmium(VIII) oxide in the presence of a cooxidant afforded 3-deoxy- or 1-deoxy-tetrofuranose-type phosphanyl sugar derivatives, respectively. cis- Dihydroxylation of 4-acyloxy-2-phospholene 1-oxide derivatives gave tetrofuranose type phosphanyl sugar derivatives. Some of these derivatives of phosphanyl sugars were subjected to structural analyses using ¹H NMR and X-ray crystallography.

     

Investigation of Novel Peptide Chiral Selectors Prepared by Solid-Phase Synthesis with a tert-Butoxycarbonyl Amino Acid

A new class of chiral stationary phases (CSP) with peptide chiral selectors was prepared by solid-phase synthesis with a tert-butoxycarbonyl-L-amino acid on silica. The type of amino acid that is favorable for this class of CSP is discussed. Using the CSP with the phenylalanine peptide selector, the effect of peptide length on the enantioselectivity was investigated in normal-phase mode. The applicability of the CSP with a phenylalanine peptide to chiral ligand-exchange chromatography was also examined.