Diacetone-mannitol

The way of designing aixi synthesizing a chiral 20-crown-6 derivative ddd-98 incorporating two 1,2-U-isopropylidene-D-mannitol residues and one 1,3 4,6-di-O-methylene-D-mannitol residue starting from appropriately constracted mono- and di-extended diacetone mannitol units is outlined (136) in Scheme 6. It relies on the local C2 symmetry of all the carbr ydrate residues and the C2 symmetry present in the final product. By developing a strategy not dissimilar to that described in Scheme 3, dithiol-bearing chiral 18-crown-6 derivatives... 

L-Mannitol does not occur naturally but is obtained by the reduction of L-mannose or L-mannonic acid lactone (80). It can be synthesized from the relatively abundant L-arabinose through the L-mannose and L-glucose cyanohydrins, conversion to the phenylhydrazines which are separated, liberation of L-mannose, and reduction with sodium borohydride (81). Another synthesis is from L-inositol (obtained from its monomethyl ether, quebrachitol) through the diacetonate, periodate oxidation to the blocked dialdehyde, reduction, and removal of the acetone blocking groups (82). 

The second diisopropylidene-D-mannitol (m. p. 122-124°) was shown by Baer, Grosheintz and Fischer49-122 180 to give rise to D-glyceraldehyde when oxidized with lead tetraacetate and then hydrolyzed, a result to be expected only from the 1,2 5,6-derivative. This structure explains too the stability of the diacetone compound towards alkaline permanganate which was reported by Karrer and Hurwitz.28... 

As an artificial enz)me, AbZyme was applied in a similar [3,3]-sigmatropic rearrangement [95,96]. The substrate 107 is prepared from a diacetone-D-mannitol through conventional synthetic transformations. On exposure to the artificial polychronal antibody in the presence of 2-(Ai-morpholino)ethanesulfonic acid and sodium chloride at 37 °C, with a molar ratio of 100 1 of the hexadiene 107 to the antibody, 107 is completely converted into the product 108 in 20 h (O Scheme 24). 

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