2,2′:5,6-Di-O-isopropylidene-2-C-hydroxymethyl-D-talono-1,4-lactone

Abstract

A second crystalline diacetonide, the title compound, C13H20O7, has been isolated from the sequential treatment of d‐tagatose with aqueous sodium cyanide, followed by acetone in the presence of acid. Structural ambiguities with regard to the size of both the lactone and ketal rings are resolved by the X‐ray crystallographic analysis.

Structure refinement: some background theory and practical strategies

“…These were replaced by partial atoms corresponding to ring-flipping. It was unclear from the actual electron density distribution which of these models was really most appropriate (Harding et al, 2005).…”

2-C-Methyl-D-allono-1,4-lactone

“…The potential of the Kiliani ascension of ketoses to provide readily available branched scaffolds has been recognized (Harding et al, 2005;Hotchkiss et al, 2004;Shallard-Brown et al, 2004); such materials are likely to be of value as a new family of chirons. A further class of branched carbohydrate building blocks may be available from the reaction of cyanide with 1-deoxyketoses, themselves prepared by addition of organometallic reagents to sugar lactones.…”

1,2:3,4-Di-O-isopropylidene-α-D-tagatofuranose

“…Its use as a dietary substitute in soft drinks and ready-to-eat cereals (Skytte, 2002) is rapidly increasing. So far, there has been little exploitation of tagatose as a chiral building block, although recently the easy preparation of branched sugar lactones by the Kiliani cyanohydrin reaction on d-tagatose has been reported ; the structures of the diacetonide products could only be firmly established by X-ray crystallographic analysis (Harding et al, 2005;Shallard-Brown et al, 2004). For a sugar to be used as a chiral starting material in organic synthesis, it must not only be cheap but also efficiently protected (Bols, 1996).…”