Enantioselective syntheses and configuration assignments of gamma-chiral butenolides from Plagiomnium undulatum: butenolide synthesis from tetronic acids.

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.