Synthesis of 11-demethyl and 6, 6, 11-demethyl calanolides A (6-9) hav been carried out by a four-step reaction sequence using a simple approach in order to investigate the structural requirements necessary for antiviral activity Synthesis of 11-demethyl and 6, 6, 11-demethyl calanolides A (6-9) hav been carried out by a four-step reaction sequence using a simple approach in order to investigate the structural requirements necessary for antiviral activity