Synthesis, crystal structure and absolute configuration of (3a,4,5,7a)-7-(but-3-en-1-yn-1-yl)-2,2-dimethyl-3a,4,5,7a-tetra-hydro-2-1,3-benzodioxole-4,5-diol.

The absolute configuration of the title compound, CHO, determined as 1,2,3,4 based on the synthetic pathway, was confirmed by single-crystal X-ray diffraction. The mol-ecule is a relevant inter-mediary for the synthesis of speciosins, ep-oxy-quinoides or their analogues. The mol-ecule contains fused five- and six-membered rings with two free hydroxyl groups and two protected as an iso-propyl-idenedioxo ring. The packing is directed by hydrogen bonds that define double planes of mol-ecules laying along the plane and van der Waals inter-actions between aliphatic chains that point outwards of the planes.