Synthesis of the Cyclobutylfuran Sector of Providencin via Zirconium-mediated Oxygen Abstraction from a Furanoside

A portion of the macrocyclic cembrenoid diterpene providencin possessing conjoined cyclobutane and furancarboxylate units was synthesized from d-glucose using deoxygenative ring contraction methodology to construct the tetrasubstituted cyclobutane and a Knoevenagel condensation of glyceraldehyde to fabricate the trisubstituted furan.