(3S,4S,5S)-4-Hydroxy-3-methyl-5-[(2S,3R)-3-methylpent-4-en-2-yl]-4,5-dihydrofuran-2(3H)-one

The title compound, C11H18O3, was synthesized to prove the relative configuration of the corresponding acyclic C1—C8 stereopentade. Molecules are linked via O—H⋯O hydrogen bonds, forming a chain along the b axis.

The title compound, C 11 H 18 O 3 , was synthesized to prove the relative configuration of the corresponding acyclic C1-C8 stereopentade. Molecules are linked via O-HÁ Á ÁO hydrogen bonds, forming a chain along the b axis.

S2. Experimental
The title compound, (I), was synthesized from the corresponding syn-aldol adduct, (II), using tetrabutylammonium fluoride (Corey & Snider, 1972) for the removal of the silyl protecting group. The subsequent lactonization proceeded in situ.
To a solution of diastereomerically pure (II) (50 mg, 0.113 mmol, 1.0 eq) in dry tetrahydrofuran (1 ml) was added TBAF (1 M in tetrahydrofuran, 0.34 ml, 3.0 eq) at 273 K. The mixture was stirred at 273 K for 25 min. The reaction was then quenched by the addition of sat. aqueous NaHCO 3 solution. The phases were separated, and the aqueous phase was extracted with CH 2 Cl 2 . The combined organic layers were dried over MgSO 4 and concentrated under reduced pressure.
Flash chromatography (isohexane/ethyl acetate 20/1 to 10/1) afforded (I) as a single diastereomer and additionally a mixture of (I) and the minor diastereomer with an overall yield of 96% (21.4 mg, 0.108 mmol) as colourless crystals.
Single crystals of (I) were obtained by vapor diffusion recrystallization technique from isohexane and ethyl acetate to

Figure 1
The molecular structure of the title compound, showing the labelling of all non-H atoms. Displacement ellipsoids are shown at the 30% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.