Azido derivatives of cellobiose: oxidation at C1 with cellobiose dehydrogenase from Sclerotium rolfsii

• Chemo-enzymatic syntheses of cellobiono azido derivatives.
• Oxidation of azido cellobiose derivatives by a bi-enzymatic system.
• Cellobiose dehydrogenase is regenerated by laccase via a redox mediator.
• Investigation of steady-state and pre-steady state kinetics and substrate docking.

We report the chemo-enzymatic synthesis of three cellobiono-1,5-lactone azido derivatives, designed as building blocks for biomedical polymer scaffolds. The synthesis is based on regioselective protection of cellobiose or 1,6-O-anhydro-β-d-cellobiose before azidation and subsequent deprotection. The oxidation to the corresponding cellobiono-1,5-lactones was investigated with 6′-azido-6′-deoxycellobiose (6′N3Clb, 5), 6-azido-6-deoxycellobiose (6N3Clb, 11) and 2-azido-2-deoxycellobiose (2N3Clb, 15) under the catalysis of cellobiose dehydrogenase (CDH) from the plant-pathogenic fungus Sclerotium rolfsii. Substrate binding characteristics and kinetics of CDH for the three cellobiose azido derivatives were studied employing computational docking, steady-state and presteady-state techniques. The process of enzymatic oxidation of the cellobiose azido intermediates was optimized by using the available kinetic information. Whereas the conversion of 15 by CDH is very slow, the conversion of 5 and 11 by a regenerated, bi-enzymatic process (CDH/redox mediator/laccase/O2) is fast, quantitative and produces azido derivatives of cellobiono-1,5-lactone in an environmentally friendly, oxygen-driven process.

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