Enzymatic aldolization technique

Catalytic aldol reactions are among the most useful synthetic methods for highly stereo-controlled asymmetric synthesis. In this account we discuss the recent development of a novel synthetic technique which uses tandem enzyme catalysis for the bi-directional chain elongation of simple dialdehydes and related multi-step procedures. The scope and the limitations of multiple one-pot enzymatic C-C bond formations is evaluated for the synthesis of unique and structurally complex carbohydrate-related compounds that may be regarded as metabolically stable mimetics of oligosaccharides and that are thus of interest because of their potential bioactivity. 

The DHAP aldolases are quite specific for the phosphorylated nucleophile 41, tvhich must therefore be prepared independently or generated in situ (cf. Section 5.4.4). Initial aldol products tvill thus contain a phosphate ester moiety, vhich facilitates product isolation, for example by barium salt precipitation or by use of ion-exchange techniques. The corresponding phosphate free compounds can be easily obtained by mild enzymatic hydrolysis using an inexpensive alkaline phosphatase at pH 8-9 [148], vhereas base-labile compounds might require vorking at pH 5-6 using a more expensive acid phosphatase [149]. 

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