Synthesis of Hybrid Cyclopeptides through Enzymatic Macrocyclization

Acknowledgements We thank Dr. G. Mann and Dr. A. Bent for supplying the enzymes and the useful discussions, and Dr. T. Lebl for the useful NMR discussions. This work was supported by the European Research Council (339367), UK Biotechnology and Biological Sciences Research Council (K015508/1), the Wellcome Trust [TripleTOF 5600 mass spectrometer (094476), the MALDI TOF-TOF Analyzer (079272AIA), 700 NMR], and the EPSRC UK National Mass Spectrometry Facility at Swansea University. J.H.N., M.A.J., and N.J.W. are named on patents that have been filed by St. Andrews and Aberdeen Universities to commercialize the enzymes (PatG) and (LynD) used in the study. No income derives from the patent.Peer reviewedPublisher PD

Stereochemical assignment of the protein-protein interaction inhibitor JBIR-22 by total synthesis

The authors acknowledge the EPSRC and Cancer Research UK (CRUK Grant No. C21383/A6950) for funding this research.Recent reports have highlighted the biological activity associated with a sub-family of the tetramic acid class of natural products. Despite the fact that members of this sub-family act as protein-protein interaction inhibitors of relevance to proteasome assembly, no synthetic work has been reported. This may be because this sub-family contains an unnatural 4,4-disubstitued glutamic acid, the synthesis of which provides a key challenge. Here we describe a highly stereoselective route to a masked form of this unnatural amino acid. This enabled the synthesis of two of the possible diastereomers of JBIR-22 and allowed its relative and absolute stereochemistry to be assigned.Publisher PDFPeer reviewe

\u3ci\u3eMedicine Meets Virtual Reality 14\u3c/i\u3e

Chapter, Real-Time Augmented Feedback Benefits Robotic Laparoscopic Training, co-authored by Nicholas Steriou, UNO faculty member. Machine intelligence will eclipse human intelligence within the next few decades - extrapolating from Moore’s Law - and our world will enjoy limitless computational power and ubiquitous data networks. Today’s iPod® devices portend an era when biology and information technology will fuse to create a human experience radically different from our own. Already, our healthcare system now appears on the verge of crisis; accelerating change is part of the problem. Each technological upgrade demands an investment of education and money, and a costly infrastructure more quickly becomes obsolete. Practitioners can be overloaded with complexity: therapeutic options, outcomes data, procedural coding, drug names etc. Furthermore, an aging global population with a growing sense of entitlement demands that each medical breakthrough be immediately available for its benefit: what appears in the morning paper is expected simultaneously in the doctor’s office. Meanwhile, a third-party payer system generates conflicting priorities for patient care and stockholder returns. The result is a healthcare system stressed by scientific promise, public expectation, economic and regulatory constraints and human limitations. Change is also proving beneficial, of course. Practitioners are empowered by better imaging methods, more precise robotic tools, greater realism in training simulators, and more powerful intelligence networks. The remarkable accomplishments of the IT industry and the Internet are trickling steadily into healthcare. The Medicine Meets Virtual Reality series can readily see the progress of the past fourteen years: more effective healthcare at a lower overall cost, driven by cheaper and better computers.https://digitalcommons.unomaha.edu/facultybooks/1236/thumbnail.jp

Covalent linking of organophosphorus heterocycles to date palm wood-derived lignin : hunting for new materials with flame retardant potential

Funding: Funding: This research was funded by EaSI-CAT at the University of St Andrews (Ph.D. studentship to D.J.D.).Environmentally acceptable and renewably sourced flame retardants are in demand. Recent studies have shown that the incorporation of the biopolymer lignin into a polymer can improve its ability to form a char layer upon heating to a high temperature. Char layer formation is a central component of flame-retardant activity. The covalent modification of lignin is an established technique that is being applied to the development of potential flame retardants. In this study, four novel modified lignins were prepared, and their char-forming abilities were assessed using thermogravimetric analysis. The lignin was obtained from date palm wood using a butanosolv pretreatment. The removal of the majority of the ester groups from this heavily acylated lignin was achieved via alkaline hydrolysis. The subsequent modification of the lignin involved the incorporation of an azide functional group and copper-catalysed azide–alkyne cycloaddition reactions. These reactions enabled novel organophosphorus heterocycles to be linked to the lignin. Our preliminary results suggest that the modified lignins had improved char-forming activity compared to the controls. 31P and HSQC NMR and small-molecule X-ray crystallography were used to analyse the prepared compounds and lignins.Publisher PDFPeer reviewe

The use of residual dipolar coupling for conformational analysis of structurally related natural products

The authors would like to acknowledge the EPSRC for funding.Determining the conformational preferences of molecules in solution remains a considerable challenge. Recently, the use of residual dipolar coupling (RDC) analysis has emerged as a key method to address this. Whilst to date the majority of the applications have focused on biomolecules including proteins and DNA, the use of RDCs for studying small molecules is gaining popularity. Having said that, the method continues to develop and here we describe an early case study of the quantification of conformer populations in small molecules using RDC analysis. Having been inspired to study conformational preferences by unexpected differences in the NMR spectra and the reactivity of related natural products, we showed that the use of more established techniques was unsatisfactory in explaining the experimental observations. The use of RDCs provided an improved understanding which, following use of methods to quantify conformer populations using RDCs, culminated in a rationalisation of the contrasting diastereoselectivities observed in a ketone reduction reactionPostprintPeer reviewe

Copper-mediated conversion of complex ethers to esters : enabling biopolymer depolymerisation under mild conditions

Authors acknowledge the China Scholarship Council (G.X. studentship), the University of St Andrews (G.X. and J.R.D.M. studentships) and the EPSRC-funded CRITICAT Centre for Doctoral Training (studentship to I.P.; EP/L016419/1) for PhD funding. C.S.L. thanks the Leverhulme Trust Early Career Fellowship (ECF-2018-480) and the University of St Andrews.Selective processing of the β-O-4 unit in lignin is essential for the efficient depolymerisation of this biopolymer and therefore its successful integration into a biorefinery set-up. An approach is described in which this unit is modified to incorporate a carboxylic ester with the goal of enabling the use of mild depolymerisation conditions. Inspired by preliminary results using a Cu/TEMPO/O2 system, a protocol was developed that gave the desired β-O-4-containing ester in high yield using certain dimeric model compounds. The optimised reaction conditions were then applied to an oligomeric lignin model system. Extensive 2D NMR analysis demonstrated that analogous chemistry could be achieved with the oligomeric substrate. Mild depolymerisation of the ester-containing oligomer delivered the expected aryl acid monomer.Publisher PDFPeer reviewe

Isothiourea-catalysed acylative kinetic resolution of aryl-alkenyl (sp2 vs. sp2) substituted secondary alcohols

We would like to thank the Engineering and Physical Sciences Research Council and CRITICAT Centre for Doctoral Training [Ph.D. studentship to S.F.M.; Grant code: EP/L016419/1 and EP/J018139/1] and The Leverhulme Trust [Early Career Fellowship to J.E.T.; ECF-2014-005] for financial support. A.D.S. thanks the Royal Society for a Wolfson Merit Award.The non-enzymatic acylative kinetic resolution of challenging aryl–alkenyl (sp2 vs. sp2) substituted secondary alcohols is described, with effective enantiodiscrimination achieved using the isothiourea organocatalyst HyperBTM (1 mol %) and isobutyric anhydride. The kinetic resolution of a wide range of aryl–alkenyl substituted alcohols has been evaluated, with either electron-rich or naphthyl aryl substituents in combination with an unsubstituted vinyl substituent providing the highest selectivity (S=2–1980). The use of this protocol for the gram-scale (2.5 g) kinetic resolution of a model aryl–vinyl (sp2 vs. sp2) substituted secondary alcohol is demonstrated, giving access to >1 g of each of the product enantiomers both in 99:1 e.r.Publisher PDFPeer reviewe

Using fractionation and diffusion ordered spectroscopy to study lignin molecular weight

This work was supported by EPSRC Ph.D. studentships EP/1654168 (JRDM). EP/1654168/1. Raw data files can be found at: https://doi.org/10.6084/m9.figshare.8034680Recent reports demonstrate that applications of the biopolymer lignin can be helped by the use of a portion of the lignin which has an optimal molecular weight range. Unfortunately, the current methods used to determine lignin’s molecular weight are inconsistent or not widely accessible. Here, an approach that relies on 2D DOSY NMR analysis is described that provides a measure of lignin’s molecular weight. Consistent results were obtained using this well-established NMR technique across a range of lignins.Publisher PDFPeer reviewe

Synthesis of indoloquinolines : an intramolecular cyclization leading to advanced Perophoramidine-relevant intermediates

We thank EPSRC (UK) for a DTA studentship for C.A.J.The bioactive natural product perophoramidine has proved a challenging synthetic target. An alternative route to its indolo[2,3-b]quinolone core structure involving an N-chlorosuccinimde mediated intramolecular cylization reaction is reported. Attempts to progress towards the natural product are also discussed with an unexpected deep-seated rearrangement of the core structure occurring during an attempted iodoetherification reaction. X-ray crystallographic analysis provides important analytical confirmation of assigned structures.Publisher PDFPeer reviewe

Structure and substrate recognition of the Bottromycin maturation enzyme BotP

JK would like to thank the University of St Andrews, which is supported by a Wellcome Trust Capital Award (086036) and the Deutsche Forschungsgemeinschaft for an Emmy Noether fellowship (KO4116/3-1). BN would like to thank the European Research Council (339367).The bottromycins are a family of highly modified peptide natural products displaying potent antimicrobial activity against Gram-positive bacteria including methicillin-resistant Staphyloccoccus aureus. Bottromycins have recently been shown to be ribosomally synthesized and post-translationally modified peptides (RiPPs). Unique amongst RiPPs the precursor peptide BotA contains a C-terminal "follower" sequence, rather than the canonical N- terminal "leader" sequence. We report the structural and biochemical characterization of BotP, a leucyl-aminopeptidase like enzyme from the bottromycin pathway. We demonstrate that BotP is responsible for the removal of the N-terminal methionine from the precursor peptide. Determining the crystal structures of apo BotP and of BotP in complex with Mn2+ allowed us to model a BotP/substrate complex and to rationalize substrate recognition. Our data represent the first step towards targeted compound modification to unlock the full antibiotic potential of bottromycin.PostprintPeer reviewe