The use of compounds comprising bicyclo-orthoester groups in coating compositions is known from U.S. patent publication No. 4,338,240. In this patent publication the use and the preparation of bicyclo-orthoester-functional compounds (hereinafter bicyclo-orthoester will be abbreviated to BOE) is described. Described are, e.g., BOE-functional compounds, which are the adduct of two compounds comprising one hydroxyl group and one BOE group and one compound comprising two isocyanate groups. The compounds are cross-linked by means of cationic ring opening homopolymerization of the BOE groups. In that case, however, the presence of moisture has to be excluded. Furthermore, energy in the form of ultraviolet, infrared or microwave irradiation or heat has to be supplied during the polymerization process.