(+)-(3aS,7aR)-Hexahydro-(3S,6R)-dimethyl-2(3H)-benzofuranone

(3aS,7aR)-HEXAHYDRO-(3S,6R)-DIMETHYL-2(3H)-BENZOFURANONE, 
3aS,7aR-hexahydro-3S,6R-dimethyl-2(3H)-benzofuranone, 
(+)-(3aS,7aR)-Hexahydro-(3S,6R)-dimethyl-2(3H)-benzofuranone (79726-51-5)

The lactone is identical to that previously reported⁴ and has the following spectral data: IR (neat) cm⁻¹: 1770, 1453, 1375, 1290, 1190, 1096, 847; 

¹H NMR (360 MHz, CDCl₃) δ: 0.99–1.38 (m, 3 H), 1.02 (d, 3 H, J = 6.5), 1.15 (d, 3 H, J = 7.6), 1.59 (m, 1 H), 1.78 (m, 2 H), 1.92 (m, 1 H), 2.25 (m, 1 H), 2.64 (quint., 1 H, J = 7.6), 4.00 (dt, 1 H, J = 11, 4); 

¹³C NMR (360 MHz, CDCl₃) δ: 9.57, 21.99, 23.77, 31.25, 34.15, 38.72 (2 carbons), 47.09, 81.38, 180.27. It has [α]_D20 +106.2° (CHCl₃, c 0.6). 

The checkers recorded [α]_D25 of +72 to +88° (CHCl₃, c 0.6). If the temperature of the distillation exceeds 110°C, a decrease in [α]_D might be observed because of epimerization α to the lactone carbonyl. If the pure diastereomer is required, it is recommended that purification be effected by column chromatography over silica gel (eluent, pentane:ethyl acetate 20:1). Typically, the lactone is obtained in a yield of55% with an [α]_D20 +149° (CHCl₃, c 1.1).

ref 4

1. Jefford, C. W.; Wang, Y. J. Chem. Soc., Chem. Commun. 1988, 634.