Production of R - and S -Mandelic Acid Derivatives

Chemical or enzymatic hydrolysis of the chiral cyanohydrin gives access to 2-hy-droxycarboxylic acids. The most prominent examples are (S)- and (R)-mandclic acids, which are mainly used for racemate resolution. Other chiral acids, such as (R)-2-chlorom an del i c acid, are used as precursors for pharmaceuticals (see Fig. 11). Scale-up and production of (R)-2-chloromandelic acid was successfully performed with a space-time yield of 250 g/L/d (ee = 95%). 

Both recombinant (R)- and (S)-HNL have been successfully used in the synthesis of chiral cyanohydrins at the plant-scale level. Their availability on a large-scale via fermentation and their striking similarities in reaction technology and chemical behavior have been crucial for the development of robust, cost-effective processes applicable to a wide variety of substrates. Exploitation of the possibilities of HNL technology has just begun. The large number of substrates and follow-up products with applications in fine chemistry reflects the attractiveness of this transformation. 

Lieberei, D. Selmar, B. Biehl, Plant Syst. Evol. 1985, 150, 49-63. 

Effenberger B. Gutterer T. Ziegler, E. Eckhart, R. Aichholz, Liebigs Ann. Chem. 1991, 47-54. 

Wagner, M. Hassiacher H. Griengl, H. Schwab, C. Kratky, Structure (London) 1996, 4, 811-822. 

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