ABSTRACT
The synthesis of bradyrhizose, the monosaccharide component of the lipopolysaccharide O-antigen of the nitrogen-fixing bacteria Bradyrhizobium sp. BTAi1 and sp. ORS278, has been achieved in 25 steps in an overall yield of 6% using myo-inositol and ethyl propiolate as the starting materials. The route involved the late-stage resolution of a racemic intermediate to provide both enantiomers of this unusual bicyclic monosaccharide. Both the natural d-enantiomer, and the unnatural and heretofore unknown l-enantiomer, were converted to disaccharide derivatives containing different forms of the monosaccharide (d,d; l,l; d,l; l,d). Evaluation of the synthetic compounds for their ability to act as microbe-associated molecular patterns in plants, through induction of reactive oxygen species, was investigated. These experiments suggest that the immunologically silent nature of the natural glycans is due to specific structural features.
Subject(s)
Immunologic Factors/chemistry , Immunologic Factors/pharmacology , Inositol/chemistry , Lipopolysaccharides/chemistry , Lipopolysaccharides/pharmacology , Monosaccharides/chemistry , Arabidopsis/drug effects , Arabidopsis/immunology , Immunity, Innate/drug effects , StereoisomerismABSTRACT
Piperazine-2,5-diones are formed by Dieckmann cyclization (NaH, THF) of substructures of the type CH(2)-N(R)C(O)CH(2)N(R')CO(2)Ph in which the terminal methylene (CH(2)) that is adjacent to nitrogen closes onto the carbonyl group of the phenyl carbamate unit at the other end of the chain. R and R' are alkyl groups, and the terminal methylene is activated by a ketone carbonyl, a nitrile, an ester, or a phosphoryl group. The starting materials are assembled by standard acylation and oxidation processes, starting from a ß-(alkylamino)alcohol, an (alkylamino)acetonitrile, an (alkylamino) ester, or an (alkylamino)methyl phosphonate.
Subject(s)
Nitriles/chemistry , Organophosphonates/chemistry , Piperazines/chemistry , Piperazines/chemical synthesis , Crystallography, X-Ray , Cyclization , Magnetic Resonance Spectroscopy , Models, Molecular , PiperazineABSTRACT
Carbonyldiimidazole (CDI) was found to mediate the Lossen rearrangement of various hydroxamic acids to isocyanates. This process is experimentally simple and mild, with imidazole and CO(2) being the sole stoichiometric byproduct. Significant for large-scale application, the method avoids the use of hazardous reagents and thus represents a green alternative to standard processing conditions for the Curtius and Hofmann rearrangements.
