Such compounds may, but need not, also belong to formula F-A. In a fourth major aspect, the compounds of the present invention are fluorinated glycosylceramide analogues, defined by the general formula F-AF: where R2 is hydrogen or an organic moiety; J is an organic moiety comprising at least one sugar unit and/or at least one Pet (pentaerythritol) unit; R3 is of the form- (Z) o-i-CF2-R3', Z is a