Synthetic approach to ryanodine; the use of O-spirodienone lactone in organic synthesis

The key steps for this synthetic approach are the preparation of o-spirodienone lactone 15, its reaction with methylvinyl ketone which gave 16 and 17, and the conversion of 16 and 17 into compound 19 by base. Finally ozonolysis of 26 followed by internal condensation gave compound 28.