5 3,4-DIHYDRO-2H,5H-PYRANO[3,2-C][1]BENZOPYRAN-5-ONE DERIVATIVES

wThe molecular structures of five 3,4-dihydro-2H,5H-pyrano[3,2-c][1]be nzopyran-5-one derivatives, namely, cis,anti-7,7a,8,9-tetrahydro-7-phe nyl-6H, H-furo-[2',3':2,3]pyrano[5,6-c][1]benzopyran-6-one [C20H16O4,( I)], cis-2-ethoxy-3,4-dihydro-4-furyl-2H,5H-pyrano [3,2-c][1]benzopyra n-5-one [C18H16O5, (II)], ro-4-phenyl-2H,5H-pyrano[3,2-c][1]benzopyran -5-one [C20H18O4, (III)], itrophenyl)-2H,5H-pyrano[3,2-c][1]benzopyran -5-one [C20H17NO6, (IV)] and methyl nyl-2H,5H-pyrano[3,2-c][1]benzopyr an-4-carboxylate [C22H20O6, (V)] have been studied by single-crystal d iffractometry. The conformation of the dihydropyran ring is compared w ith that found in 36 entries in the Cambridge Structural Database [ver sion of 28 February 1997; Alien & Kennard (1993). Chem. Des. Autom. Ne ws, 8, 31-37]. A scatterplot of the conformation of 46 independent mol ecules is shown. These molecules present a more or less distorted half -chair conformation, with few exceptions; in particular, it seems that molecules with a second ring fused to the dihydropyran moiety adopt a diplanar conformation.