Lipase-catalysed enantioselective kinetic resolution of rac-lipidic alkynylcarbinols and a C5 synthon thereof via a hydrolysis approach

Lipase-mediated kinetic resolution (LMKR) of three racemic lipidic alkynylcarbinol (LAC) acetates, rac-heptadeca-1,4-diyn-3-yl acetate (rac-2-Ac), rac-heptadeca-1,4,6-triyn-3-yl acetate (rac-3-Ac) and rac-heptadeca-1-yn3yl acetate (rac-4-Ac), besides the versatile C-5 synthon dialkynylcarbinol (DAC) acetate, rac-(triisopropylsilyl) penta-1,4-diyn-3-yl acetate (rac-5), was studied. CAL-B immobilized on acrylic resin was investigated as catalyst on LMKR of rac-2-5-Ac. Fourteen commercial lipases (immobilized and free forms), besides one esterase, were also investigated on the LMKR of rac-5-Ac. After investigation of reaction parameters, optimal conditions were established for each compound, yielding both (R)- and (S)-alcohols in 50 % conversions, enantioselectivities (E) > 200 and high e.e. values [(R)-2 and (S)-2-Ac, e.e. > 99%; (R)-3 and (S)-3-Ac, e.e. 98 %; (R)-4 and (S)-4-Ac, e.e. 96 %; (R)-5 and (S)-5-Ac, e.e.> 99 %]. Except for rac-5-Ac that had Thermomyces lanuginosus immobilized on immobead-150 as best catalyst, CAL-B was the most efficient lipase on LMKR of rac-2-4-Ac. (S)-Alcohols were obtained by lipase-mediated hydrolysis of (S)-acetate compounds, using CAL-B for (S)-4-Ac (57.5 % yield and e.e. 96 %) and lipase from Candida rugosa for (S)-5-Ac (53 % yield and e.e. > 99 %).