Threo diols

The reaction of Pt(C03)(dppp)] with a modest excess of vicinal diols in CH2C12 solution affords the corresponding [Pt(a,/3-diolato)(dppp)] species under equilibrium conditions, a reaction that is readily reversed by the addition of dry ice to the product. The reaction with triols such as glycerol and alditol carbohydrates also affords the corresponding diolato species, with the reaction exhibiting excellent equilibrium regioselectivities for a number of isomers, of which the 7, 6-threo diols are the most favored. 

Scheme 4-21 shows the preparation of L-threitol and L-erythritol.38 Epoxy alcohols (2J ,3iS)-61 and (2S,3/ )-61. generated by asymmetric epoxidation, are exposed to sodium benzenethiolate and sodium hydroxide in a protonic solvent to undergo base-catalyzed rearrangement, yielding the threo-diol 62 and erythro-diol 63, which can then be converted to the corresponding tetraacetate of l-threitol 67 and L-erythritol 69 through subsequent transformations. 

One of the first applications of the microbial hydrolysis of epoxides for the synthesis of a bioactive compound is based on the resolution of a 2,3-disub-stituted oxirane having a cis-configuration (Scheme 14). Thus, by using an enzyme preparation derived from Pseudomonas sp., the (91 ,10S)-enantiomer was hydrolyzed in a frans-specific fashion (i.e. via inversion of configuration at C-10) yielding the 9R,10R)-threo-diol. The remaining (9S,101 )-epoxide was converted into (-1-)-dispar lure, the sex pheromone of the gypsy moth in >95% ee [101]. 

Oleic acid was converted to the erythro diol 264 or the threo diol 258 by reaction with permanganate or hydrogenperoxide respectively. The threo compound 258 was converted to the 9,11-dioxahomoprostanoids. Reaction with paraformaldehyde formed 259 or 260, phosgene converted the diol into 261 whereas reaction with thiophosgene gave compound 262. 

The reagent is also suitable for reduction of aldehydes and ketones.3 Thus the stereoselective reduction of the acetamino ketone (2) to the threo diol (3) was effected by means of calcium borohydride in 70% yield 4... 

Sodium borohydride gave a mixture of the threo diol (25% yield) and the erythro diol (47% yield). 

Stereoselective Carbonyl Reductions. L-selectride reduction of U-acyl-Y-lactones has been shown to furnish the syn-reduction products in good yield and high diastereoselection which may be hydrolysed to threo-diols. The stereochemistry appears to be largely independent of the size of the acyl group and is in accord with reduction following the Felkin-Ahn transition-state model (Scheme 2). ... 

Although the stereochemical course of the Corey-Winter reaction is implicit in the diagrams above, we have not addressed the issue explicitly. The process is stereospecific the diol undergoes overall syn elimination. Thus, etythro diols typically lead to a Z alkene, and threo diols to an E alkene. The threo E case is shown in the example below ... 

Li X, Tanasova M, Vasileiou C, Borhan B (2008) Fluorinated porphyrin tweezer a powerful reporter of absolute configuration for erythro and threo diols, amino alcohols, and diamines. J Am Chem Soc 130(6) 1885-1893... 

The s-trans and the s-cis diastereomer obtained this way are in situ oxidized with retention of the configuration to provide 384 and 385 respectively. In the third protocol of this type of diol formation the hydride reduction is juxtaposed to a Grignard reaction to prepare the eryikro- and the threo-diols 386 and ... 

The mild periodate oxidation of 3- and 6-O-substituted 2-acetamido-2-deoxy-D-galactitols and 4- and 6-O-substituted D-glucitols have been studied, and the major sites of oxidation shown as expected to be threo-diol moieties. The products were characterized by ms of thin layer chromatography samples of the corresponding 1,2-di-0-palmitoyl-sn-g/ycerD-3-phosphoethanolamine derivatives. 

Using another EH overexpressed in Y. lipolytica (Oxy-10), the kinetic resolution of an epoxyamide was performed at 50% conversion, resulting in the optically pure residual (R,i )-epoxide and the formed threo-diol with )delds of 32% and 22%, respectively [102] (Figure 8.33). The remaining (K,K)-epoxide is of synthetic interest, because it is used for the S5mthesis of the a-mannosidase inhibitor (-)-swainsonine. 

Applications of the aldol method are not restricted to carbohydrates or carbohydrate-derived materials, despite obvious advantages. This was impressively illustrated, e.g., by FruA-based chemoenzymatic syntheses of the insect pheromone (+)-ejc< -brevicomin (76 Fig. 26) [141,142]. Due to the fact that the (/ ,i )-configurated threo-diol substitution pattern, which is masked in the bicyclic structure of 76 as an intramolecular acetal but comprises the only independent stereogenic centers of brevicomin, is symmetrical to chain... 

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