Taihei Nishiyama

Synthesis of Glycocinnasperimicin D

The first total synthesis of amino sugar antibiotic glycocinnasperimicin D (1) has been achieved by a convergent, three-component coupling strategy. The key steps involve the Heck-Mizoroki reaction by using the iodophenyl glycoside 50 and acryl amide 32 to furnish the right core structure of 1, and the construction of the urea glycoside employing the reaction of glycosyl isocyanate 8 with amino sugar 9. Glycosyl isocyanate 8 was prepared by the oxidation of isonitrile 10, which displayed excellent reactivity in the coupling event. Synthetic roadblocks, encountered during this synthetic effort, have led to the development of the alpha-selective, Lewis acid catalyzed phenyl glycosylation process with 2-amino-hexopyranose and a procedure for acetonide deprotection without affecting the silyl ethers.

Glucopyranosyl isocyanates as versatile glycosylating reagents for the preparation of neoglycoconjugates

A new and simple synthetic method for the preparation of glucopyranosyl isocyanates has been developed. This method establishes a convenient access to the urea- and carbamate-tethered neoglycoconjugates starting from glucopyranosyl isocyanates.