Synthesis of 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] and derivatives: precursors of long-chain polyketides

Racemic 1,1′-methylene(1RS,1′RS,3RS,3′RS,5RS,5′RS)-8-oxabicyclo3.2.1]oct-6-en-3-ol] ((±)-6) derived from 2,2′-methylenedifuran has been resolved kinetically with Candida cyclindracea lipase-catalysed transesterification giving 1,1′-methylenedi(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo3.2.1]oct-6-en-3-ol] (?)-6 (30% yield, 98% ee) and 1,1′-methylenedi(1S,1′S,3S,3′S,5S,5′S)-8-oxabicyclo3.2.1]oct-6-en-3-yl] diacetate (+)-8, (40% yield, 98% ee). These compounds have been converted into 1,1′-methylenedi(4S,4′S,6S,6′S)- and (4R,4′R,6R,6′R)-cyclohept-1-en-4,6-diyl] derivatives.