While chitooligosaccharides (COs) derived from fungal chitin are potent elicitors of defense reactions, structurally related signals produced by certain bacteria and fungi, called lipo-chitooligosaccharides (LCOs), play important roles in the establishment of symbioses with plants. Understanding how plants distinguish between friend and foe through the perception of these signals is a major challenge. We report the synthesis of a range of COs and LCOs, including photoactivatable probes, to characterize a membrane protein from the legume Medicago truncatula. By coupling photoaffinity labeling experiments with proteomics and transcriptomics, we identified the likely LCO-binding protein as LYR3, a lysin motif receptor-like kinase (LysM-RLK). LYR3, expressed heterologously, exhibits high-affinity binding to LCOs but not COs. Homology modeling, based on the Arabidopsis CO-binding LysM-RLK AtCERK1, suggests that LYR3 could accommodate the LCO in a conserved binding site. The identification of LYR3 opens up ways for the molecular characterization of LCO/CO discrimination.

[structure: see text] Hsp90 has recently emerged as a promising biological target for treatment of cancer. Herbimycin A and other members of the benzoquinoid ansamycin class of natural products are known to inhibit Hsp90 activity. The total synthesis of herbimycin A was achieved from the commercially available Roche ester 1 by using allylmetals to control the stereogenic centers at C6, C7, C10, C11, and C12 and a ring-closing metathesis to control the (Z)-double bond of the (E,Z)-dienic moiety.

No abstract

[reaction: see text] Treatment of beta,gamma-unsaturated monoprotected 1,2-diols with diethylaminosulfur trifluoride (DAST) allows the stereoselective formation of beta,gamma-unsaturated aldehydes in good yields and with a good transfer of chirality.

+)-Preussin was synthesized in ten steps with an overall yield of 6.4% from phenylacetaldehyde. The three stereogenic centers were controlled by enantioselective allyltitanations of aldehydes.

Antibiotics U 1200 Total Synthesis of Herbimycin A. -The title compound is a promising agent for anticancer treatment. -(CANOVA, S.; BELLOSTA, V.; BIGOT, A.; MAILLIET, P.; MIGNANI, S.; COSSY*, J.; Org. Lett. 9 (2007) 1, 145-148; Lab. Chim. Org., CNRS, Ec. Super. Phys. Chim. Ind., F-75231 Paris, Fr.; Eng.) -R. Steudel 21-194

Aldehydes P 0170Rearrangement of Homoallylic Alcohols Induced by DAST. -DAST induce a stereo-and enantioselective rearrangement of unsaturated monoprotected 1,2-diols to give α-substituted β,γ-unsaturated aldehydes stereoselectively in good yields. -(CANOVA, S.; BELLOSTA, V.; MIGNANI, S.; BIGOT, A.; COSSY*, J.; Org. Lett. 8 (2006) 10, 2091-2094; Lab. Chim. Org., CNRS, F-75231 Paris, Fr.; Eng.) -R. Steudel 37-057