The known aldehyde methyl
2,3,4-tri-O-methyl-α-D-gluco-hexodialdo-1,5-pyranoside
(9) was converted in eight steps into the 6-phenyl glucose-derived enolic
ortho ester (Z)-1,6-dideoxy-1,1-ethylenedioxy-
2,3,4-tri-O-methyl-6-phenyl-D-xylo-hex-5-enopyranose
(22), the geometry of which was established by a single-crystal X-ray study.
Treatment of the 6-phenyl enolic ortho ester (22) with titanium tetrachloride
at –78° effected clean rearrangement into
(2R/S,4R,5R,6S)-3,3-ethylenedioxy-4,5,6-trimethoxy-2-phenylcyclohexanone
(26). Reaction of (22) with methylmagnesium iodide gave
(1R,2S,4R,5S,6S)-3,3-ethylenedioxy-4,5,6-trimethoxy-1-methyl-2-phenylcyclohexanol
(24), the structure and stereochemistry of which were established by an X-ray
study. Reaction of (22) with phenylmagnesium bromide gave (25), the 1-phenyl
analogue of (24). The firmly established structure of (24) led to proof both
chemically and by X-ray means that the product from reaction of
1,6-dideoxy-1,1-ethylenedioxy-2,3,4-tri-O-methyl-D-xylo-hex-5-enopyranose
(5) with methylmagnesium iodide has the hydroxy acetal structure (7) rather
than the originally assigned hemiacetal structure (3).
