Synthesis, Crystal Structure, and Herbicidal Activity of (3R,4R)-4,7,7-Trimethyl-6-oxabicyclo [3.2.1] octane-3,4-diol Mono-fatty Acid Esters

Four mono-fatty acid esters (Ia similar to d) were synthesized via the esterification of (3R,4R)-4,7,7-trimethyl-6-oxabicyclo[3.2.1]octane-3,4-diol (I) with fatty acid chlorides (CH3(CH2)(n) COC1, n = 0, 2, 4, 6) and structurally characterized by means of H RMS, IR, H-1-1-NMR, C-13-NMR and X-ray diffraction. Compounds Ia similar to d all belong to monoclinic system, P2(1/c) space group. Intermolecular O(2)-H(2)center dot center dot center dot O(1) hydrogen bonds, intramolecular O(2)-H(2)center dot center dot center dot O(3) hydrogen bonds and van der Waals' interaction between fatty acid ester groups link each of the mono-fatty acid ester molecules into a bilayer structure similar to liposome with the exposed hydrophobic moiety and the sandwiched lipophilic moiety. Especially, compounds Ia similar to d could be dissoluble or scattered in aqueous solution and showed hydrophilic/lipophilic property-dependent herbicidal activity against the dicotyledon plant rape (Brassica campestris) and the monocotyledon plant barnyard grass (Echinochloa crus galli). At the concentration of 10 mmol.L-1, the inhibition rates of compounds Ia-d against the root growth of rape are 31.9, 90.8, 99.5 and 100%, respectively and the inhibition rates against the shoot elongation of barnyard grass are 19.3, 50.0, 80.2 and 100%, respectively.