TMG-chitotriomycin,a unique tetrasaccharide disclosed recently by Kanzaki and coworkers from the culture filtrate of Streptomyces anulatus NBRC 13369,exhibits potent and selective inhibition against the-N-acetylglucosaminidase(GlcNAcase) of insect and fungal but no activities against the enzyme of human and plant.1 This unique inhibitory spectrum could lead to new insights into understanding of the molecular mechanisms of the important chitin-degrading systems occurring in a wide variety of organisms and the development of new antifungal and insecticidal agents.Here we discuss the total synthesis and structural revision of this natural product,2 the synthesis of its shorter and longer congers,and their structure-activity relationships.3 The new glycosylation method with glycosyl ortho-hexynylbenzoates as donors and a Au(Ⅰ) as catalyst shall be highlighted in the synthesis of these chitooligosaccharide derivatives.