Elsevier

Bioorganic & Medicinal Chemistry

Volume 19, Issue 3, 1 February 2011, Pages 1236-1241
Bioorganic & Medicinal Chemistry

An efficient synthesis of the precursor of AI-2, the signalling molecule for inter-species quorum sensing

https://doi.org/10.1016/j.bmc.2010.12.036Get rights and content

Abstract

Autoinducer-2 (AI-2) is a signalling molecule for bacterial inter-species communication. A synthesis of (S)-4,5-dihydroxypentane-2,3-dione (DPD), the precursor of AI-2, is described starting from methyl glycolate. The key step was an asymmetric reduction of a ketone with (S)-Alpine borane. This new method was highly reproducible affording DPD for biological tests without contaminants. The biological activity was tested with the previously available assays and compared with a new method using an Escherichia coli reporter strain thus avoiding the use of the pathogenic Salmonella reporter.

Introduction

(S)-4,5-Dihydroxypentane-2,3-dione (DPD) 1 is the uncyclized precursor of AI-2, a signalling molecule for bacterial inter-species communication.1, 2 DPD is a reactive 1,2-diketone which in aqueous medium forms an equilibrium mixture of the linear form and two anomeric cyclic forms 2 and 3, their hydrated versions 4 and 5 (Scheme 1).3 The hydrated isomer 4 can exist also as its 2,3-borate diester 6. It has been shown that distinct bacteria can detect different forms of this molecule and thus all these forms are known collectively as AI-2. Specifically, many Vibrio have the LuxP-type of AI-2 receptor which recognizes 6,4 whereas members belonging to phylogenetically distinct families such as the human pathogens Salmonella typhimurium and Bacillus anthracis as well as the plant symbiont Sinorhizobium meliloti contain the LsrB-type of receptors and recognize the non-borated diastereoisomer 5.3, 5

Bacterial populations use cell–cell communication in order to coordinate their behaviour and function in such a way that they can adapt to changing environments. Chemical communication among bacteria is called ‘quorum sensing’. Examples of quorum sensing behaviours are biofilm formation, virulence-factor expression, antibiotic production and bioluminescence.6 AI-2 is unique in that it is produced and detected by a wide variety of bacteria.2, 7 Thus, using AI-2 bacteria are able to detect the presence of other bacterial species in their vicinity and regulate gene expression according to the species composition in the environment.8 Ultimately, the understanding of the molecular mechanisms that bacteria use to regulate their behaviours can lead to the development of new therapies to control bacterial infections, and also to develop biotechnological applications for the control of industrial scale production of beneficial bacterial products, such as antibiotics or recombinant proteins.

Although a small molecule, DPD is highly functionalised, optically active and highly reactive. This presents a significant synthetic challenge and the production of reasonable quantities presents many problems. The absence of an accessible synthesis of DPD has been a major drawback in studies aimed at the understanding of AI-2 quorum sensing.7 In this work we describe an efficient and economic method to synthesise DPD on a reasonable scale. We have also developed a simple procedure to remove the last protective group thus furnishing uncontaminated DPD solutions.

Section snippets

Results and discussion

Currently, there are five published9, 10, 11, 12, 13 syntheses of DPD but all have problems and hence were considered unsuitable for the routine production of larger quantities required for biological studies. These routes generally use optically active starting materials and in most cases glyceraldehyde, derived from sugars. Each presented chemical or practical problems and we reasoned that a route in which the asymmetric centre was produced by the asymmetric reduction of a ketone could

Conclusion

In conclusion, (R)- and (S)-DPD were obtained in 8 steps with a 33% overall yield and >98% ee using a common strategy. Synthetic (S)-DPD proved to have the same biological activity as that of the enzymatically produced DPD. All intermediates were easy to handle and presented low volatility and excellent stability, the reactions were very reproducible and afforded high yields. Liberation of DPD from acetal 15 with Dowex resin and washing with chloroform allowed us to obtain a final DPD

General

1H NMR spectra were obtained at 400 MHz in CDCl3 or D2O with chemical shift values (δ) in ppm downfield from tetramethylsilane in the case of CDCl3, and 13C NMR spectra were obtained at 100.61 MHz in CDCl3 or D2O. Assignments are supported by 2D correlation NMR studies. Flash column chromatography: silica gel Merck 60, 0.040–0.063 mm (230–400 mesh ASTM). Analytical TLC: Aluminium-backed silica gel Merck 60 F254. Specific rotations ([α]D20) were measured using an automatic polarimeter. Reagents and

Acknowledgements

We acknowledge the generous financial support provided by Fundação para a Ciência e Tecnologia (PPCDT/DG/BIA/82010/2006 Portugal). We thank CERMAX for the use of the NMR spectrometers, which were purchased within the framework of the National Programme for Scientific Re-equipment, contract REDE/1517/RMN/2005, with funds from POCI 2010 (FEDER) and Fundação para a Ciência e a Tecnologia (FCT). We thank Pedro Lamosa for help in quantifying the DPD samples by NMR and Paula Chicau for help with HPLC

References and notes (24)

  • K.B. Xavier et al.

    Curr. Opin. Microbiol.

    (2003)
  • S.T. Miller et al.

    Mol. Cell

    (2004)
  • M. Frezza et al.

    Tetrahedron Lett.

    (2005)
  • M. Kadirvel et al.

    Bioorg. Med. Chem. Lett.

    (2010)
  • C.A. Lowery et al.

    Bioorg. Med. Chem. Lett.

    (2005)
  • C.A. Lowery et al.

    Chem. Soc. Rev.

    (2008)
  • X. Chen et al.

    Nature

    (2002)
  • C.S. Pereira et al.

    J. Bacteriol.

    (2009)
  • C.M. Waters et al.

    Annu. Rev. Cell Dev. Biol.

    (2005)
  • K.R. Hardie et al.

    Nat. Rev. Microbiol.

    (2008)
  • K.B. Xavier et al.

    Nature

    (2005)
  • M.M. Meijler et al.

    Angew. Chem., Int. Ed.

    (2004)
  • Cited by (41)

    • Synthesis of D-desthiobiotin-AI-2 as a novel chemical probe for autoinducer-2 quorum sensing receptors

      2019, Bioorganic Chemistry
      Citation Excerpt :

      Although we are able to efficiently synthesise the enantiomeric pure form of DPD [23], in this work we synthesised the racemic form to avoid the exclusion of any new receptor which might recognise different DPD adducts. The alkylation of the Weinreb amide 4 [23] with propyne 3 afforded the ketone 5 in 90% yield (Scheme 1). The non-stereoselective reduction of ketone 5 with NaBH4 gave alcohol 6 that after protection with the silyl group afforded the alkyne 7 in excellent yield.

    • Synthesis and biological activity of a potent optically pure autoinducer-2 quorum sensing agonist

      2019, Bioorganic Chemistry
      Citation Excerpt :

      So, here we describe an optimised synthesis process for the pure S-enantiomer of C4-propoxy-HPD ((4S)-20) and C4-ethoxy-HPD analogues ((4S)-25). We took advantage of our previous work as we have previously reported the enantioselective syntheses of (4R)- and (4S)-DPD starting from methyl glycolate, where the optically enriched alcohol 15 was the key intermediate [13]. The optically pure enantiomer (4S)-20 was the most efficient compound having approximately double the activity of DPD.

    View all citing articles on Scopus
    View full text