Sugar-Based Polyesters: From Glux-Diol Synthesis to Its Enzymatic Polymerization

This work details the synthesis of 2,4:3,5-di-<i>O</i>-methylene-d-glucitol (glux-diol), a bicyclic acetal derivative of d-glucose obtained from d-glucono-1,5-lactone, and also explores its subsequent polymerization to produce biobased polyesters. Key steps for the synthesis of glux-diol are (i) protection with paraformaldehyde, (ii) Fischer esterification, and (iii) reduction with lithium aluminum hydride (LiAlH₄). A new purification method was developed to effectively remove inorganic salt byproducts, which can hinder polymerization. The sugar-based monomer was then copolymerized with C4-C10 dimethyl esters using <i>Candida antarctica</i> lipase B as a biocatalyst in Cygnet 2.0, a green, high-boiling solvent. The biocatalytic polycondensation produced oligomers with number-average molecular weights (<i>M</i> _n) between 900 and 2200 g mol^-1. These materials exhibited thermal stabilities ranging from 391 to 419 °C, with the specific temperature depending on the molecular weight, degree of polymerization, and the carbon chain length of the chosen diester. Overall, this integrated approach, which combines efficient sugar functionalization with biocatalysis, offers a promising pathway for the synthesis of novel biobased polyesters.