2-Methylpropane-l,3-diol

The GMT in human serum reacts most rapidly with Y-glutamyl-p-nitroanilide at pH 8.2. The same activity is found in 2-amino-2-methylpropane-l 3 diol, diethanolamine, triethanolamine and tris buffers. Magnesium ions have no effect on the activity but favor the solubilization of the substrate. Bondar and Moss (54) found that free glutamate, due to elevated serum glutamate concentrations or glutamate released by substrate breakdown, increases the apparent GMT activity. They concluded that the assay should be performed in the presence of 1.0 vM/1 glutamate in order to reduce the possibility of falsely elevated results. This was not observed by others. Rowe and co-workers have indicated that certain batches of p-nitroanilide substrate contain impurities which may reduce GMT activity and increase the values ( ). Huesby and Stromme (56) confirmed the presence of such impurities and recommended pyridine extraction for substrate purification. 

Summary Metriol is conveniently prepared by reacting 2-(hydroxymethyl)-2-methylpropane-l,3-diol with 90% nitric acid in the presence of concentrated sulfuric acid. The reaction is generally brief, and the resulting mixture is then treated with ice, and allowed to stand. The next day, the mixture is mixed with diethyl ether to dissolve the oily product, and this resulting ether mixture is then washed, dried, and then evaporated to remove the ether and recover the oily product. 

Epoxide Hydrolase-catalyzed Synthesis of (/ )-3-Benzyloxy-2-methylpropane-l,2-diol... 

Bacillus subtilis, engineered to overproduce epoxide hydrolase, was used as a whole-cell biocatalyst to resolve racemic 1-benzyloxymethyl-1-methyloxirane with high (5)-selectivity. The remaining (/ )-epoxide was subsequently ring opened in situ, with inversion of stereochemistry, to obtain highly enantiomerically enriched (/ )-3-benzyloxy-2-methylpropane-l,2-diol in greater than 50 % theoretical yield (Figure 5.2). 

This was dissolved with Et20 (82 mL), cooled slowly to —30 °C and kept at that temperature for 6 h. Mother liquor was decanted off under suction and the crystals collected were rinsed twice with cold Et20. The crystals were directly dried in vacuo without any washing to afford (f )-3-benzyloxy-2-methylpropane-l,2-diol (2.1 g, 52 % recovery) as colorless fine needles m.p. 30-31 °°C. 

Benzyloxy-2-methylpropane-l,2-diol, a desymmetrized form of 2-methylpropane-1,2,3-triol with its terminal hydroxy being protected as a benzyl ether, was prepared using the B. subtilis epoxide hydrolase-catalyzed enantioselective hydrolysis of the racemic benzyloxymethyl-l-methyloxirane readily available from methallyl chloride and benzyl alcohol. The preparation of the racemic epoxide, a key intermediate, was described in Procedures 1 and 2 (Sections 5.6.1 and 5.6.2), its overall yield being 78 %. The combined yield of enantiomerically pure (7 )-3-benzyloxy-2-methylpropane-l,2-diol was 74 % from ( )-benzyloxymethyl-l-methyloxirane, as described in Procedures 3-5 (Sections 5.6.3 and 5.6.5), with the overall procedures leading to the biocatalytic dihydroxylation of benzyl methallyl ether . 

In the Mukaiyama variation of the aldol reaction, 3-benzoyloxy-2-trimethylsiloxy-l-butene adds to 2-methylpropanal in a stereoselective manner. Best results are obtained in the presence of titanium(IV) chloride, giving the adducts 9/10 in a diastereomeric ratio of 92 8. Hydrolysis of the benzoyl group and subsequent oxidative cleavage of the 1,2-diol moiety liberates / -hy-droxycarboxylic acids593. 

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