“…(S)-(+)-5 was also prepared from [4R )-4-methyl-6oxoheptanoic acid (9) whose absolute configuration has been determined. 36,37 The absolute stereochemical assignment at the 5 position of these lactones, and, thus, the complete stereochemical assignment of the four 3,5-dimethylvalerolactone enantiomers was established by a detailed analysis of their nmr, 13C nmr, and CD spectra. In addition, the cis and trans lactones 7 and 8, resectively, were shown to possess the half-chair conformations 7A and 8A, respectively.…”