Lipo-Chitooligosaccharidic Nodulation Factors: Synthesis and Agricultural Perspectives

Abstract

Lipo-chitooligosaccharidicnodulation(Nod)factorsproducedbyrhizobiaareaclassofsignallingmoleculesthatinduceasymbioticassociationbetweenlegumesandsoilbacteriarhizobialeadingtotheformationof thenitrogen-fixingrootnodule.TheyconsistofachitinoligomericbackboneN-acylatedatthenon-reducingunit andareequippedwithavarietyofsubstituentsatbothendsoftheoligosaccharide.Thisbriefaccountfocuses onthedifferentapproachesdevelopedfortheirsynthesiswithparticularemphasisonglycosylationmethods. CurrentuseoftheseNodfactorsoranalogsasadditivesinagriculturalapplicationshasshowntobeverypromisingforsustainableagriculture.

Synthesis of the Fungal Lipo‐Chitooligosaccharide Myc‐IV (C16:0, S), Symbiotic Signal of Arbuscular Mycorrhiza

“…LCO Myc factors could also be used to stimulate root system development, which is essential to improve water and mineral uptake, especially in parts of the world where soil fertility and water availability are poor. These remarkable biological activities prompted us to develop a new chemical synthesis of Myc factors using new tools in oligosaccharide chemistry and learning from past syntheses26 of Nod factors. Thus we considered: (i) selection of a suitable glycosylation procedure able to cleanly and efficiently produce the difficult (β1–4) glycosidic bonds between two 2‐acetamido‐2‐deoxy‐ D ‐glucopyranosyl units; (ii) choice of an oligomerization strategy that would provide the oligosaccharide with the highest efficacy; (iii) selective differentiation of identical functional groups, e.g., primary or secondary hydroxy and amino groups present in the chitin fragment.…”

From Chitin to Bioactive Chitooligosaccharides and Conjugates: Access to Lipochitooligosaccharides and the TMG‐chitotriomycin

“…The N‐acetyl moiety presents, however, three major limitations in any reconstruction procedure: the solubility of acetamido‐containing building blocks is poor, 2‐acetamido‐2‐deoxy glycosyl donors are usually impractical donors because of the formation of the relatively stable 1,2‐ O , N ‐oxazoline intermediates,6 and 2‐acetamido‐2‐deoxy glycosyl acceptors are notoriously poor nucleophiles, especially the 4‐hydroxy group of GlcNAc derivatives 7. 8 Given the importance of COSs, a wide range of glycosylation procedures integrated in stepwise or blockwise assembly strategies have been developed for the effective construction of these oligomeric motifs from monomeric glucosamine precursors 5c. 7e, 9, 10…”

“…For the initial use of these NHTFA building blocks, we prepared glycosyl acceptors, which are useful in the synthesis of the lipochitooligosaccharides5 or analogues,5c, 10c, 19 with a free hydroxy group at C4 of the reducing unit. Standard anomeric acetate cleavage,20 silylation,21 deacetylation, benzylidene formation, acetylation, and reductive opening of the acetal in CH 2 Cl 2 with triethylsilane and trifluoroacetic acid22 gave acceptors 11 and 12 in respective overall yields of 57 and 53 % from 6 and 7 (Scheme ).…”

Selective Modification of Chitin and Chitosan: En Route to Tailored Oligosaccharides

“…The use of chitooligosaccharides (COS) has also attracted the attention of the scientific community owing to their numerous biological activities . Fascinatingly, COS can present different degrees of polymerization (DP), degrees of N‐acetylation (DA), and patterns of N‐acetylation (PA) and consequently trigger different biological responses .…”