Enantiomers (2S, 4S)- and (2R, 4R)-3-(naphthalene-1-ylmethyl) pentane-2,4-diols were synthesized by the reduction of (Z)-4-hydroxy-3-(naphthalene-1-ylmethyl) pent-3-en-2-one with NaBH4 in methanol (MeOH). Crystallization in dichloromethane of this racemic mixture led to simple crystals with a crystalline habit with similar morphologies; however, in a group of them, it was possible to find a barely observable difference that allowed determining a crystal structure for each of the enantiomers, the 2S,4S, and the 2R,4R.

The stereochemistry of two new 1,3‐diol curcuminoid derivatives, ((3R*,5R*)‐3,5‐dihydroxyheptane‐1,7‐diyl) bis (2‐methoxy‐4,1‐phenylene) diacetate namely rac‐6, its acetylated derivative, (3R*,5R*)‐1,7‐bis(4‐acetoxy‐3‐methoxyphenyl) heptane‐3,5‐diyl diacetate (rac‐7) and the diastereomeric model compound 1,3‐bis(4‐methoxyphenyl)‐1,3‐propanediol (rac‐2) were investigated through their X‐ray crystal structures and nuclear magnetic resonance spectra. Achiral compounds diacetylcurcumin (4) and diacetylcurcumin‐4H (5), crystallized in the Sohncke space group P21 allowed its unambiguous stereochemical assignment. The unit cell of tetraacetylated compound rac‐7 consists of a co‐crystal of two conformers and constitute a rare case of conformational isomorphism composed by TTTTTT and TTTTGT conformers in a 1:1 stoichiometric proportions. The antioxidant activity of each pair of derivatives was investigated and a significant difference in activity was found for tetraacetylated pairs rac‐7/(3R,5 S)‐1,7‐bis(4‐acetoxy‐3‐methoxyphenyl) heptane‐3,5‐diyl diacetate (meso‐7) and cyclic sulfites (((4R*,6R*)‐2‐oxido‐1,3,2‐dioxathiane‐4,6‐diyl) bis (ethane‐2,1‐diyl)) bis (2‐methoxy‐4,1‐phenylene) diacetate (rac‐8)/(((4 S,6R)‐2‐oxido‐1,3,2‐dioxathiane‐4,6‐diyl) bis (ethane‐2,1‐diyl)) bis (2‐methoxy‐4,1‐phenylene) diacetate (meso‐8). The present study addresses the stereochemistry and biological activity of these types of compounds.