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The synthesis and stereochemistry of the first reported pentaspiro- and hexaspiro-1,3-dioxane and polyspiro-1,3-oxathiane (from dispiro to hexaspiro) derivatives are described. The crystal structures of a dispiro- and tetraspiro-1,3-oxathiane were determined by X-ray diffraction methods. NMR and...
Synthesis of the terminal disaccharide unit of a novel α-(1→2) linked heptoglycan of K. pneumoniae ssp. strain R20 from methyl α- d -mannopyranoside has been presented. Central to the strategy is the application of Sharpless asymmetric dihydroxylation to introduce a new center at C-6 position...
Straightforward and rapid access to 2-arylbenzo( b )thiophenes has been developed. It involved a catalytic coupling of 3-activated benzo( b )thiophenes with several aryl halides in the presence of a phosphine-free palladium system. In case of fragile functional groups such as aldehydes, a...
The influence of the metal ion and chiral diamine used to form a metal(salen) complex on the catalytic activity of the complex in the asymmetric benzylation of an alanine enolate was investigated. Only metal ions which could form square-planar complexes gave catalytically active complexes, and...
Aminals, which are used as protecting groups in syntheses and are part of many biologically active compounds, are normally prepared from aldehydes and diamines under conditions that remove water in order to shift the equilibrium to the side of the aminal. Here we report for the first time that...
The separation of diastereomeric esters derived from (±)-pyridylethanols and 3β-acetoxyetienic acid were achieved by an extraction technique using diethyl ether and aqueous hydrochloric acid. A formal total synthesis of PNU-142721 was effectively carried out to prepare the chiral, non-racemic...
Using the HMO approximation, bond energy equations for triangular three-centre, two-electron (3 c -2 e ) bonded species AB 2 + (π-complexes) and the isomeric systems (AB−B + , BB−A + , BA−B + and A + +BB) are described. The electronegativity difference (Δ χ ) between the atoms or...
Chromene derivatives bearing oxymethyl-12-crown-4 ( 1 ), -15-crown-5 ( 2 ), -18-crown-6 ( 3 ) ether moieties, and non-cyclic analogue ( 4 ) were synthesized, and their metal ion binding properties and photochromism were examined. NMR titration with alkali metal ions revealed that 1 formed a 1:2...
A new synthetic method of (−)-vallesamidine, including a unique 2,2,3-trialkylindoline skeleton, was developed by reductive radical cyclization reaction from the 2,3-dialkylindole derivative, which has been known to be an intermediate for the synthesis of aspidospermidine.
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