The subject invention provides ginkgolide C derivatives compounds having the structure: ##STR00001## wherein R is H or -A-Ar, where A is an alkyl group; and Ar is an aryl group, which may contain heteroatoms and may be unsubstituted or substituted by one to five substituents each selected from the group consisting of hydrogen, alkoxy, --CH.sub.2CO.sub.2R.sup.4, and --CH.sub.2CONR.sup.5R.sup.6; where R.sup.4 is an alkyl group; and R.sup.5 and R.sup.6 are each, independently, hydrogen or a branched or unbranched alkyl group; wherein R.sup.1 is H or --COR.sup.7, where R.sup.7 is alkyl, aryl or amino; wherein R.sup.2 is present or absent, and when present is H, --COR.sup.8 or --CO--Z--R.sup.8; where R.sup.8 is alkyl, aryl or amino; and Z is oxygen; wherein R.sup.3 is present or absent, and when present is --COR.sup.9; where R.sup.9 is alkyl or aryl; wherein only one of R.sup.2 or R.sup.3 is present in the compound; wherein only two of R, R.sup.1, R.sup.2 and R.sup.3 are H; and wherein each of a and b designates a single covalent bond which is present or absent, where bond a is present when R.sup.3 is absent and bond b is present when R.sup.2 is absent; or an optically pure enantiomer of the compound. Additionally, the subject invention provides methods of inhibiting the activity of a glycine receptor using these compounds.