Vinylogous esters and amides: Useful synthons for diversity-oriented and natural product synthesis

The first total synthesis of boehmeriasin A was achieved in seven steps from readily available materials with an overall yield of 29%. The absolute stereochemistry of the natural product was determined to be of the (R)-configuration. (-)-(R)-Boehmeriasin A demonstrated potent cytotoxicity in several cancer cell lines including drug resistant cancer cells where paclitaxel is inactive.;An efficient and mild method for the construction if chromones was developed that requires only a single purification step at the end of the sequence and results in moderate to good yields of the isolated chromones. This method was applied toward the synthesis of 5-hydroxy-2-(2-phenylethyl)chromone, a neuroprotective chromone.;The reduction of tertiary amides using Cp2Zr(H)Cl to the corresponding aldehydes on a preparatory scale results in good isolated yields of the products. Through a modified workup procedure, issues not previously observed were overcome to afford good isolated yields of the corresponding aldehydes.