Convenient Synthesis of 3-Glycosylated Isocoumarins
A new route for the synthesis of 3-substituted and 8-hydroxy-3-substituted isocoumarins was developed by modified Julia olefination for initial C–C bond formation between aldehydes and benzylic sulfones. Palladium-catalyzed Meinwald rearrangement was used as a key step for the obtainment of ketone intermediates, which – upon base-promoted intramolecular cyclization – afforded the desired isocoumarins. The developed method paves the way to hitherto unknown 3-glycosylisocoumarins, in general, and 3-glucosylisocoumarins, in particular, wherein the glucosyl moiety is attached to the pyrone ring of the isocoumarin framework.
Sudarshan, Kasireddy,Aidhen, Indrapal Singh
p. 34 - 38
(2017/01/13)
DIASTEREO- AND ENANTIOSELECTIVE SYNTHESIS OF 1,2-DIOLS BY VANADIUM(II) PROMOTED PINACOL CROSS COUPLING
The V(II) promoted pinacol cross coupling of a chiral aromatic aldehyde with achiral aliphatic aldehydes occurs to afford syn diols in up to 91:9 diastereoisomeric ratio and up to 84percent enantiomeric excess.The pinacol coupling of (S)-lactaldehyde and (R)-glyceraldehyde derivatives has also been studied and matching and mis-matching pairs have been identified.The stereochemistry of the products was established by correlation.The sense and degree of stereoselection is discussed.