接着在甲苯和乙腈的混合溶剂中，三氟乙酸的催化作用下，中间体与甲醛发生反

Then in a mixed solvent of toluene and acetonitrile, under the catalysis of trifluoroacetic acid, the intermediate reacts with formaldehyde to obtain compound 4, which constructs the basic skeleton of the natural product. After a simple functional group transformation, Complete synthesis.

Then in the mixture solvent of toluene and acetylene, under the catalytic action of teflon acetic acid, the intermediate reacts with formaldehyde, obtains compound 4, builds the basic skeleton of natural products, and completes the synthesis after a simple transformation of the function group.

Then in the mixed solvent of toluene and acetonitrile, under the catalysis of trifluoroacetic acid, the intermediate reacts with formaldehyde to obtain compound 4, which constructs the basic framework of natural products. After a simple functional group transformation, the total synthesis can be completed.