RhuA catalyzed aldol reactions

An interesting problem in stereoisomerism is found in the aldol reactions of the achiral aldehydes which are obtained by ozonolysis of the homoallylic alcohols 174. After stereospecific conversion by the FruA [230], the products can be readily induced to form an intramolecular glycoside 175 by acidic (R=OH) or alkaline treatment (R=C1), under which conditions the two equatorial ring hydroxyl groups completely direct the stereogenic acetal formation [234]. The corresponding RhuA catalyzed reactions deliver the enantiomeric... 

Figure 19.3 DHAP-aldolase catalyzed aldol addition of DHAP to N-Cbz-aminoaldehydes. Reaction conversion to aldol adduct in gel emulsion (black bars) and dimethylformamide/ water 1 4 system (gray bars) for reactions catalyzed by (a) RAMA, (b) RhuA and (c) FucA.

Scheme 16.4 RhuA wild type-catalyzed aldol addition reactions of DHAP to N-Cbz piperidine carbaldehyde derivatives for the synthesis of indolizidine and quinolizidine iminocycli-tols. (a) RhuA wild-type catalyst (b) dephosphorylation by acid phosphatase and (c) Pd/C.

Scheme 16.5 RhuA wild type- and RhuA mutant-catalyzed aldol additions reactions of DHA to (S)- and (R)-N-Cbz-alaninal (14a,b), N-Cbz- and N-formyl-glycinal (14c,d). (a) RhuA wild type and RhuA ° mutant and (b) Pd/C.

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