The synthesis of higher carbon sugars: a study on the rearrangement of higher sugar allylic alcohols

The C12 higher sugar enone 15 (prepared from the corresponding phosphonate and aldehyde) was highly stereoselectively reduced to the d-glycero-allylic alcohol. The epimeric l-glycero-isomer was obtained by the non-selective reduction of the higher enone under Luche conditions. The separate treatment of both allylic alcohols with triflic anhydride provided the corresponding triflates, which in situ underwent allylic rearrangement with the elimination of one of the benzyl groups (from the aldehyde part of the molecule). The stereochemical aspects of this transformation are also discussed.

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2,3,4-Tri-O-benzyl-d-glucitolSource of chirality: chiral poolAbsolute configuration: (2S,3R,4R,5R)[α]D = +12.8 (c 1, CHCl3)

1,2,3,4-Tetra-O-benzyl-d-glucitolSource of chirality: chiral poolAbsolute configuration: (2S,3R,4R,5R)[α]D = +14.4 (c 1, CHCl3)

Methyl 2,3,4,9,10,11,12-hepta-O-benzyl-7,8-dideoxy-7,8-didehydro-l-xylo-α-d-gluco-dodec-7(E)-eno-1,5-pyranosid-6-uloseSource of chirality: chiral poolAbsolute configuration: (1S,2R,3S,4R,5S,9R,10S,11S)[α]D = +3.9 (c 1, CHCl3)

Methyl 2,3,4,9,10,11,12-hepta-O-benzyl-7,8-dideoxy-7,8-didehydro-l-xylo-α-d-glycero-d-gulo-dodec-7(E)-eno-1,5-pyranosideSource of chirality: chiral poolAbsolute configuration: (1S,2R,3S,4R,5R,6R,9R,10S,11S)[α]D = +23.6 (c 1, CHCl3)

Methyl 2,3,4,9,10,11,12-hepta-O-benzyl-7,8-dideoxy-7,8-didehydro-l-xylo-α-l-glycero-d-gulo-dodec-7(E)-eno-1,5-pyranosideSource of chirality: chiral poolAbsolute configuration: (1S,2R,3S,4R,5R,6S,9R,10S,11S)[α]D = +4.4 (c 1, CHCl3)

2,5-Anhydro-1,3,4,6-tetra-O-benzyl-l-iditolSource of chirality: chiral poolAbsolute configuration: (2S,3R,4R,4S)[α]D = +31.7 (c 1, CHCl3)

2,5-Anhydro-1,3,4,6-tetra-O-benzyl-l-glucitolSource of chirality: chiral poolAbsolute configuration: (2S,3R,4R,4R)[α]D = +24.6 (c 1, CHCl3)