Hisashi Uda

Absolute stereostructures of halenaquinol and halenaquinol sulfate, pentacyclic hydroquinones from the okinawan marine sponge Xestospongia sapra, as determined by theoretical calculation of CD spectra

The absolute stereostructures of two pentacyclic hydroquinones, halenaguinol (1) and halenaquinol sulfate (2) from the Okinawan marine sponge Xestospongia sapra, have been determined by means of theoretical calculation of CD spectra.

Highly diastereoselective reduction of chiral β-ketosulphoxides under chelation control: application to the synthesis of (R)-(+)-n-hexadecano-1,5-lactone

The presence of zinc chloride in the reduction of chiral β-ketosulphoxides with di-isobutylaluminium hydride effects high 1,3-asymmetric induction to give β-hydroxysulphoxides; this method can be successfully applied to the synthesis of optically pure 1,4- or 1,5-lactones.

Highly enantiofacial protonation of prochiral lithium enolates with chiral β-hydroxy sulfoxides

Abstract Highly enantioselective protonation of prochiral lithium enolates is disclosed. The present method employed ( S,R s )-CF 3 -hydroxy sulfoxide (3b) as the chiral protonating agent, and the protonation of lithium enolates of cyclohexanone derivatives with 3b proceeded with high enantioselectivities.

A chiral probe useful for optical resolution and X-ray crystallographic determination of the absolute stereochemistry of carboxylic acids

Abstract (1S,2R,4R)-(−)-2,10-Camphorsultam is a very useful chiral probe for optical resolution by HPLC and X-ray crystallographic determination of the absolute stereochemistry of carboxylic acids. The absolute configurations of 2,6-dimethylspiro[3.3]heptane-2,6-dicarboxylic acid and [2.2]paracyclophane-4-carboxylic acid are determined.

Generation of 3-Carbanion Species from 3-Phenylsulfinyl- and 3-Phenylsulfonyl Propionic Acids

Abstract During the course of studies on butenolide synthesis1 we have investigated the utilities of 3-sulfur-functionalized propionic acid derivatives. We report the results with 3-carbanion species obtained from 3-phenylsulfiny1- and 3-phenylsulfonylpropionic acids (1) and (2). These compounds were easily prepared from 3-phenylthiopropionic acid.

New route to enantiomerically pure 4,4-Disubstituted cyclohex-2-en-1-ones: Asymmetric synthesis of (+)-mesembrine

Abstract Enantiomerically pure β,β-disubstituted vinyl sulfoxides undergo cycloaddition with dichloroketene to give β,β-disubstituted γ-lactones which are transformed into synthetically important 44-disubstituted cyclohex-2-enones in optically pure form. The present method is applied to the synthesis of enantiomerically pure (+)-mesembrine.

Synthesis and absolute stereochemistry of (+)-adociaquinones A and B

Abstract Adiciaquinones A (+)-1 and B (+)-2 were synthesized and their absolute configurations were determined to be (14bS).

Synthesis, circular dichroism and absolute stereochemistry of chiral spiroaromatic compounds. 9,9′-Spirobifluorene derivatives

The chiral spiroaromatic compounds (+)-2 and (+)-3 with 9,9′-spirobifluorene skeletons have been synthesized and their absolute stereostructures have been unambiguously determined to be R, by application of the CD exciton chirality method; the R absolute stereochemistry of (–)-[6,6]-vespirene 1 was established by chemical correlation with these compounds.

Absolute stereochemistry of 1-(9-phenanthryl)-2-naphthoic acid as determined by CD and X-ray methods

Abstract 1-(9-Phenanthryl)-2-naphthoic acid ( 1 ) is optically resolved as the (1 S ,2 R ,4 R )-(−)-2,10-camphorsultam amide ( 5 ) by HPLC. The absolute stereochemistry of acid (+)- 1 is determined to be (a S ) by CD and X-ray studies.

Revision of the structure of raphanusanins, phototropism-regulating substances of radish hypocotyls

Abstract The structures of raphanusanins A and B, growth inhibitors involved in phototropism of radish hypocotyls, were determined by X-ray crystallographic structure analysis and by spectral studies to be (3R*,6R*)- and (3R*,6S*)-3-[methoxy(methylthio)methyl]-2-pyrrolidinethione, respectively. Therefore, the previously proposed structure of these compounds of 2-piperidinethione skeleton should be revised.