The work which is described in this thesis is principally concerned with X-ray crystallography. Some other work, which Involved molecular orbital calculations, was also carried out and is described in Appendix I. Three compounds in all were studied by X-ray diffraction techniques, and the results of these investigations are summarised below. (1) Dimethylcertierocin: This compound, which has the formula CH3O.CO.(CH.CH)6.COOCH3, and which is the dimethyl ester of an acid isolated from a fungus, crystallises as yellow needles from chloroform. The crystals are triclinic, space goup C1 1 P 1 or C1 1 - P 1, and the unit cell dimensions are a = 9.06, b = 7.52, c = 6.07 A; alpha= 104.8, beta= 104.
