Synthesis of Sugar-Derived 2′- and 3′-Substituted Furans and Their Application in Diels−Alder Reactions

Abstract

A convenient synthesis of 2′- and 3′-furyl sugars in which the furan and the sugar parts are directly connected is presented. The key step comprises HF·py-induced cyclization of α,β-unsaturated carbonyl compounds (ketones or aldehydes) possessing terminal hydroxymethylene groups protected as TBDPS ethers. Treatment of such furan derivatives with N-phenylmaleimide under high-pressure conditions (11 kbar) produces the corresponding [4+2] adducts, with the endo forms predominating. At p = 1 atm and T = 20 °C, however, the exo isomers are formed as the main products. The [4+2] adducts undergo retro Diels−Alder reactions at elevated temperatures at atmospheric pressure.