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Synthesis of bacterial glycoconjugates
Our lab developed an efficient protocol to synthesize rare bacterial amino and deoxy monosaccharide building blocks, including DATDH, bacillosamine, fucosamine, and AAT. In this strategy, changing the sequence of addition of nucleophiles in a series of one-pot double serial and double parallel displacement reactions using azide, phthalimide and nitrite ions as nucleophiles and mannose derived 2,4-bistrifluoromethanesulfoniates (triflates) as electrophiles enabled rapid access to various orthogonally protected rare deoxy amino sugar building blocks. The orthogonally protected rare sugar building blocks were stereoselectively assembled to access a variety of conjugation-ready bacterial O-glycans. We also carried out synthesis of deoxy amino L-sugar containing oligosaccharides. Unprecedented access to the rare sugars has now allowed biological studies in collaboration with Prof. Peter H. Seeberger (immunological evaluation of bacterial glycans for vaccine development), Dr. Daniel Dube (metabolic incorporation of azide containing rare sugars in bacteria), Prof. Jerry Eichler (N-glycosylation in Archaea), and Prof. Cristina de Castro, Prof. Alba Silipo (University of Naples, Italy).
Chemical synthesis of trehalose containing glycolipids & oligosaccharides
Several trehalose containing glycans are present mainly in mycobacteria including MTb and also in fungi and worms. Synthesis of disymmetrically substituted trehalose derivatives is a formidable task due to challenges involved in regioselective protections and stereoselective 1,1-a,a-glycosylation. Over past few years, we have developed efficient methodologies to functionalize the eight hydroxyl groups of trehalose in a highly regioselective manner. The dissymmetric derivatives so obtained have been utilized in the total synthesis of various antigens including maradolipids, sulfolipids, Ac2SGL, triesters of trehalose, emmyguyacins, nonasaccharide OSE1 and others.
C-glycoside synthesis
Our laboratory has accomplished total synthesis of C-galactosyl ceramide as a potent inhibitor of HIV-1 and C-glycosyl amino acids as GalCer mimics.
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