Keywords: Asymmetric dihydroxylation / Butyrolactones / β,γ-Unsaturated carboxylic esters / Stereoselective synthesis / Wolff rearrangement β,γ-Unsaturated esters with stereodefined trisubstitued C=C double bonds were prepared by the Arndt-Eistert homologation of α,β-unsaturated carboxyl halides, by two-step methoxycarbonylation of allylbarium reagents, by deconjugation of α,β-unsaturated esters, and by Horner-Wadsworth-Emmons variants of the Stobbe condensation. Sharpless asymmetric dihydroxylation of the β,γ-unsaturated esters, followed by spontaneous cyclization, afforded β-hydroxy-γ-lac-

Both enantiomers of the gamma-chiral alpha,beta-dimethylated butyrolactones nat-1 and nat-2 from the moss Plagiomnium undulatum were synthesized stereoselectively through butenolides and tetronic acids, respectively. The configuration of the natural products was determined by GLC comparisons with mono(3-O-acetyl-6-O-tert-butyldimethylsilyl-2-O-methyl)hexakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin as a stationary phase.

2006 Furan derivatives R 0060Asymmetric Dihydroxylation of β,γ-Unsaturated Carboxylic Esters with Trisubstituted C=C Bonds -Enantioselective Syntheses of Trisubstituted γ-Butyrolactones. -The starting β,γ-unsaturated esters are prepared as geometrically pure (E)and (Z)-isomers. Their Sharpless asymmetric dihydroxylation reactions are accompanied by spontaneous cyclization to provide β-hydroxy-γ-lactones in moderate to good yields and enantioselectivities. Two series are performed using either (DHQD) 2 -PHAL or (DHQ)2-PHAL. -(KAPFERER, T.; BRUECKNER*, R.; Eur. J. Org. Chem. 2006, 9, 2119-2133; Inst. Org. Chem. Biochem., Albert-Ludwigs-Univ., D-79104 Freiburg/ Br., Germany; Eng.) -Klein 33-124

En route to a comprehensive set of hydroxylactone building blocks (4R,5R)-, (4R,5S)-, (4S,5R)-, and (4S,5S)-5a, Sharpless asymmetric dihydroxylations of allylic chlorides (E)- and (Z)-9 were performed. They delivered the four stereoisomers of diol 10 with up to 92% ee and absolute configurations, which were proven to be in accordance with the Sharpless mnemonic.

Substituted benzothiazoles play an important role in medicinal chemistry due to their pharmacological properties. Their 2-substituted derivatives are often prepared from 2-chlorobenzothiazoles, which in turn can be synthesized from the 2-mercapto precursor using sulfuryl chloride. In practice, this seemingly straightforward and widely used reaction can be impeded by poor reproducibility and low reaction yields. In this communication, we report that the simple addition of water to the reaction leads to remarkable improvements in reaction efficiency. We attribute this effect to the formation of acid through partial hydrolysis of sulfuryl chloride. This hypothesis is supported by the observation that improved yields were also obtained in the presence of some anhydrous acidic additives. The simple combination of sulfuryl chloride and water reproducibly provides excellent yields for a range of chlorinated products.