Synthesis of (±)‎-6,8-dimethoxy-3- pentadecylisochroman, its 1-hydroxy derivative and (±)‎-3,4-dihydro-6,8-dimethoxy-3- pentadecylisocoumarin related to peniolactol

Abstract EN

Straightforward high yield syntheses of the 6,8-dimethoxy-3-pentadecyl- isochroman (5), 6,8-dimethoxy-3-pentadecyl-l-hydroxyisochroman (6b) and hence of 3,4-dihydro-6,8-dimethoxy-3-pentadecylisocoumarin (7), related to the fungal metabolite peniolactol (lab) are reported.

Since direct cyclocondensation of 1 -(3,5- dimethoxyphenyl)heptadecan-2-ol (2,R=H) invariably afforded the bis-isochroman (8), the alcohol was converted to the formyl acetate (3).

Reduction of compound (3) afforded the hydroxymethyl acetate (4) which on hydrolysis gave isochroman (5).

Direct hydrolysis of formyl acetate (3) afforded the 1-hydroxyisochroman (6b) which was readily oxidized to the dihydroisocoumarin (7).