A process according to claim 2 wherein (3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-ol is reacted with bis-(4-nitrophenyl)carbonate before coupling to compound of formula (5).

A method for the synthesis of hexahydro-furo[2,3-b]furan-3-ol of formula (7) starting from an intermediate of formula (1) wherein P<sup>1 </sup>and P<sup>2 </sup>represent each independently a hydrogen, a hydroxy-protecting group or may together form ng group, transforming said intermediate of formula (1) into a nitromethane derivative of formula (3) wherein R¹ represents alkyl, aryl or aralkyl, R² represents hydrogen or C(═O)OR³, R³ represents alkyl, aryl or aralkyl, or R³, if present, and R¹ taken together with the atoms to which they are attached may form a 6 to 8-membered cyclic group which may be optionally substituted with alkyl, aralkyl, or aryl, subsequently transforming said nitromethane derivative into a tetrahydrofuran derivative of formula (6) wherein OR⁴ represents an alcoholate, and then transforming the intermediate of formula (6) into hexahydro-furo[2,3-b]furan-3-ol of formula (7) by way of an intramolecular cyclisation reaction view more