First Isolation and Stereochemistry of Optically Active Telluroxides

Optically active telluroxides 1 and 2 were isolated for the first time by means of medium-pressure liquid chromatography using an optically active column. Absolute configuration of the telluroxides (+)-1 and (+)-2 was determined to be R based on their specific rotations and circular dichroism spectra. The configurational lability and mechanism for racemization via an achiral hydrate were clarified by kinetic study and isotope tracer experiment.     

First Direct Synthesis of Optically Active 3-Methylcyclopentene

(?)-(S)- and (+)-(R)-3-methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis. The (S)-configuration for (?)-1 was confirmed by correlation with (?)-(S)-1-methylindane.     

Axial Configuration of Optically Active Colchicinoids and Allocolchicinoids: A Correction

Correction of the axial configuration of (−)-rotating colchicinoids and allocolchicinoids from (aS) to (aR) is reported.     

The First Example of Optically Active Chlorophosphine: T-Butylphenylphosphinochlorioite

Abstract

In general, alkylthiophosphonium salts can react with nucleophiles both in the sense of the Arbusov rearrangement (a) and the exchange of alkylthio groups at the P atom (b). We have recently demonstrated¹ that in the case of highly “thiophilic” nucleophiles such as mercaptide anions or tris(N, N-dimethylamine)phosphine the reactive centre is the sulphur atom (c).     

Total Synthesis and Absolute Configuration Assignment of MRSA Active Garcinol and Isogarcinol

A short total synthesis of (±)‐garcinol and (±)‐isogarcinol, two endo‐type B PPAPs with reported activity against methiciline resistant Staphylococcus aureus (MRSA), is presented. The separation of framework‐constructing from framework‐decorating steps and the application of two highly regio‐ and stereoselective Pd‐catalysed allylations, that is, the Pd‐catalysed decarboxylative Tsuji–Trost allylation and the diastereoselective Pd‐catalysed allyl–allyl cross‐coupling, are key elements that allowed the total synthesis to be accomplished within 13 steps starting from acetylacetone. After separation of the enantiomers the absolute configurations of the four natural products (i.e., (?)‐garcinol, (+)‐guttiferone E (i.e., ent‐garcinol), (?)‐isogarcinol, and (+)‐isoxanthochymol (i.e., ent‐isogarcinol)) were assigned based on ECD spectroscopy.     

Absolute Configuration of Gilmaniellin

The absolute configuration of dechlorogilmaniellin ( 2 ) could be determined from its chiroptical data by applying coupled-oscillator theory to the CD couplet around 272 nm and from the sign of its n →π^* Cotton effect. Gilmaniellin ( 1 ) has the same absolute configuration.     

Absolute Configuration of Actinioerythrin

The CD. correlation of (3 S, 3′S)-and (3 R, 3′R)-actinioerythrol diacetate, obtained by total synthesis from β-ionone, with actinioerythrin isolated from the sea anemone Actinia equina L. shows that the natural compound has the (3 S, 3′S)-configuration.