A Scalable Synthesis of 1-Cytosinyl-N-malayamycin A:  A Potent Fungicide

A stereocontrolled synthesis of 1-cytosinyl-N-malayamycin A, an N-analogue of the naturally occurring malayamycin A with fungicidal activity, is reported. The approach was designed to rely solely on substrate control for introduction of the required stereochemistry, avoiding the use of chiral reagents or auxiliaries. Formation of the N-nucleoside was achieved through the activation of a thioglycoside, proceeding via sulfonium and thionium intermediates. Ring closure metathesis was used to build the bicyclic perhydrofuropyran heterocycle.