Gingerol synthesis

Diels-AIder reactions, I, 618 reactions, 1, 617-620 synthesis, 1, 614-616 2-Germoxetanes heterosubstituted germacyclobutanes and, 1, 596 Gewald synthesis thiophenes, 4, 888-889 ( )-Gingerol synthesis, 1, 453 (+)-(S)-Gingerol synthesis, I, 435 Ginkgolide A... 

ZO107 Denniff, P., and D. A. Whiting. Bio-synthesis of (6) gingerol, pungent principle of Zingiber officinale. Chem Commun 1976 711. 

Based on the recent impressive progress made on asymmetric hydrolysis, the design and bio-transformation of the optically active ethyl 2,2-difluoro-3-hydroxyoctanoate 78 and synthesis of optically active fluorinated [6]-gingerol derivatives are reported [82]. The following criteria were used in the search for a practical route to chiral ethyl 2,2-difluoro-3-hydroxyoctanoate with a high -value (1) the search of an additive to enhance the enantioselectivity of asymmetric hydrolysis by lipases, and (2) the modification of ethyl 2,2-difluoro-... 

The (R)-enantiomer of (242) has also been prepared and used as a chiral auxiliary in an enantioselective aldol synthesis of (+)-(S )-gingerol (79CB3703). (R )-Glutamic acid (246) was thus converted into (i )-pyroglutamic acid by simply heating in water. Conversion of (247) to its methyl ester and LAH reduction delivered alcohol (248). Ethyl nitrite treatment of (248) gave nitrosoamine (249), which was methylated to furnish (250). Exposure of (250) to LAH completed the synthesis of the required chiral auxiliary RAMP [(R)- l-amino-2-(methoxymethyl)pyrrolidine]. The hydrazone (252), derived from RAMP and acetone, was... 

Another important contribution is to the regioselectivity of enolate formation from unsym-metrical ketones. As we established in chapter 13, ketones, particularly methyl ketones, form lithium enolates on the less substituted side. These compounds are excellent at aldol reactions even with enolisable aldehydes.15 An application of both thermodynamic and kinetic control is in the synthesis of the-gingerols, the flavouring principles of ginger, by Whiting.16... 

Aldol-type condensation of chiral a-sulfinyl hydrazones with aldehydes also provides a route leading to chiral 3-hydroxy ketones. - This is exemplified by the synthesis of (-)-(/ )-[6]-gingerol (98 equation 24). ... 

Aldol reactions with specific enol equivalents Contrast with equilibrium methods Aldols with Lewis acid catalysis silyl enol ethers Application to the synthesis of gingerol Reaction at O or C Silylation, Acylation and Alkylation Naked enolates... 

An application of this process is seen in the synthesis of ( )-[6]-gingerol (1 equation 10). In this example, the regioselectivity of deprotonation is 92% at C-1 and 8% at C-3. With the weaker base lithium hexamethyldisilazane, the C-l C-3 ratio is only 3 1. The method has also been used to prepare nine other ( )-gingerols. 

Chiral a-sulfinyl dimethylhydrazones form stabilized carbanions that can be used in enantioselective aldol reactions. A typical example is shown in equation (21). Removal of the chiral sulfur auxiliary is accomplished by reductive desulfurization. Under these conditions recovery and reuse of the sulfur moiety is impossible. Synthetic and optical yields reported for these aldol reactions are modest in most cases. However, in a direct comparison to the SAMpMaMP methodology, Annunziata has prepared (-)-(/ )-[6]-gingerol in 60% finders prior synthesis had yielded this aldol product in 36% ee. ... 

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