L - rhamnulose - 1 - phosphate and L - fuculose - 1 - phosphate aldolases mediated multi - enzyme cascade systems for

One-pot multistep stereoselective cascade reactions were implemented for the straightforward synthesis of various nitrocyclitols. Two kinases, an aldolase and a phosphatase were involved in this process together with a spontaneous intramolecular Henry reaction to provide a nitrocyclitol moiety. The C-C bond formation catalyzed by the aldolase and the nitroaldol reaction were key steps to build the carbocycle stereoselectively. The acceptor substrates for aldolases were all 4-nitrobutanal structurally based, hydroxylated or not on C2 and/or C3 positions. On the one side, L-fuculose-1-phosphate aldolase (FucA) has catalyzed the formation of the expected (R,R; D-erythro) aldol except in the case of 4-nitrobutanal from which (R,S; L-threo) aldol was also present. On the other side, L-rhamnulose-1-phosphate aldolase has always provided the expected (R,S; L-threo) aldol together with minor amount of (R,R; D-erythro) aldol thus being less stereoselective than FucA. The intramolecular Henry reaction has occurred spontaneously on the aldol due to the presence of both ketone and terminally positioned nitro group. This cyclisation was stereoselective and correlated to the presence or not of a hydroxyl group in β to the nitro group. From 4-nitrobutanal as substrate and for one defined stereochemistry by the aldolase (R,R or R,S) one cyclitol was formed. In the other cases, two diastereomeric series were formed due to the presence of an R and S configured alcohol function in β to the nitro group. The combination of this set of reactions successfully furnished 11 nitrocyclitols never described before in literature.