From the fronds of Costarican fern Odontosoria gymnogrammoides CHRIST (Pteridaceae), a phenolic glycoside 'odontoside (I)', was isolated together with protocatechuic acid, protocatechualdehyde, orientin (II) and 6"-O-acetyl orientin (III, a new compound). The structure of I was unequivocally established by comparing 13C nuclear magnetic resonance spectra of I and 3, 4-dimethoxybenzyl dimethylprotocatechuate, which was synthesized by the macrolidelactonization method using cesium carbonate from dimethylprotocatechuic acid and 3, 4-dimethoxybenzyl alcohol.
