A method according to claim 1 which method further comprises a) epimerizing with acid intermediate of formula β-(4) into the intermediate of formula α-(4); and <chemistry id="CHEM-US-00050" num="00050"><img id="EMI-C00050" he="29.38mm" wi="62.31mm" img-content="chem" img-format="tif"/> b) crystallizing intermediate of formula α-(4) with a solvent prior to the reduction thereof. view more

A method according to claim 3 which method further comprises after crystallizing intermediate of formula α-(4), a) epimerizing with acid intermediate of formula β-(4) in the mother liquor of said crystallization into the intermediate of formula α-(4); and b) crystallizing intermediate of formula α-(4) with a solvent; prior to the reduction thereof. view more

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

A method according to claim 1 wherein the intermediate of formula (3) is transformed into an intermediate of formula (6) by making use of a Nef reaction.

A method according to claim 1 for the synthesis of hexahydro-furo[2,3b]furan-3-ol of formula (7.1) starting from an intermediate of formula (1), wherein P<sup>1 </sup>and P<sup>2 </sup>taken together form an isopropylidene,</claim-text> <chemistry img id="EMI-C00064" he="20.57mm" wi="23.11mm" file="US07126015-20061024-C00064.TIF" alt="embedded image" img-content="chem" img-format="tif"/> condensing said intermediate of formula (1) resulting in an intermediate of formula (2), wherein P¹ and P² taken together form an isopropylidene, R² represents —C(═O)OR³, wherein R³ is methyl and R¹ is methyl, reacting said ester of formula (2) into a nitromethane derivative of formula (3) wherein P¹ and P² taken together form an isopropylidene, R² represents —C(═O)OR³, wherein R³ is methyl, and R¹ is methyl, transforming said intermediate of formula (3) using a base and subsequently an acid to yield intermediates of formula (4) and (4′), wherein R² represents —C(═O)OR³, wherein R³ is methyl, R¹ is methyl and R⁴ is methyl, decarboxylating intermediates of formula (4) leading to an intermediate of formula (5), wherein R⁴ is methyl, reducing said intermediate of formula (5) with a suitable reducing agent resulting in an intermediate of formula (6), wherein R⁴ is methyl, transforming the intermediate of formula (6) into compound 7.1 by way of intramolecular cyclization reaction view more

A method according to claim 1 wherein R<sup>1 </sup>and R<sup>3 </sup>each independently are C<sub>1-6</sub>alkyl, aryl or arylC<sub>1-6</sub>alkyl or together with the atoms to which R<sup>1 </sup>and R<sup>3 </sup>are attached form a 6 to l, aryl or arylC_1-6alkyl, and wherein R⁴ is C_1-6alkyl. view more

A method according to claim 1 wherein R<sup>1</sup>, R<sup>3 </sup>and R<sup>4 </sup>each independently are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl or pentyl.

A method according to claim 1 wherein P<sup>1 </sup>and P<sup>2 </sup>together form an acid labile vicinal-diol protecting group.

A method according to claim 1 wherein P<sup>1 </sup>and P<sup>2 </sup>is a dialkyl methylene radical.