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Natural product synthesis remains one of the most vibrant and intellectually rewarding areas of chemistry, although the justifications for pursuing it have evolved over time. In the early years, the emphasis lay on structure elucidation and confirmation through synthesis, as exemplified by celebrated studies on cocaine, morphine, strychnine and chlorophyll. This was followed by a phase where the sheer demonstration that highly complex molecules could be recreated in the laboratory in a rational manner was enough to justify the economic expense and intellectual agonies of a synthesis. Since then, syntheses of natural products have served as platforms for the demonstration of elegant strategies, for inventing new methodology ‘on the fly’ or to demonstrate the usefulness and scope of methods established with simpler molecules. We now add another aspect that we find fascinating, viz. ‘natural product anticipation’. In this Review, we survey cases where the synthesis of a compound in the laboratory has preceded its isolation from nature. The focus of our Review lies on examples where this anticipation of a natural product has triggered a successful search or where synthesis and isolation have occurred independently. Finally, we highlight cases where a potential natural product structure has been suggested as a result of synthetic endeavours but not yet confirmed by isolation, inviting further collaborations between synthetic and natural product chemists. Natural products and their synthesis have always fascinated organic chemists, frequently providing the inspiration and testing ground for new synthetic methods. This Review considers examples of natural products that were prepared first synthetically and predicted to be natural products prior to their isolation from nature.

The pseudopterosins are a family of diterpene marine natural products, which, by virtue of their interesting anti-inflammatory and analgesic properties, have attracted the attentions of many synthetic chemists. The most efficient syntheses reported to date are 14 and 20 steps in the longest linear sequence for chiral pool and enantioselective approaches, respectively, and all start with precursors that are easily mapped onto the natural product structure. Here, we describe an unconventional approach in which a chiral cross-conjugated hydrocarbon is used as the starting material for a series of three cycloadditions. Our approach has led to a significant reduction in the step count required to access these interesting natural products (10 steps chiral pool and 11 steps enantioselective). Furthermore it demonstrates that cross-conjugated hydrocarbons, erroneously considered by many to be too unstable and difficult to handle, are viable precursors for natural product synthesis. The pseudopterosins are a family of natural products whose interesting anti-inflammatory and pain-relieving properties have inspired many synthetic approaches. Now, an unusual approach that starts with an axially chiral hydrocarbon that engages in a triple Diels–Alder sequence has been shown to result in the shortest total synthesis of a pseudopterosin so far.

The fungal-derived bicyclo[2.2.2]diazaoctane alkaloids are of interest to the scientific community for their potent and varied biological activities. Within this large and diverse family of natural products, the insecticidal metabolite (+)-brevianamide A is particularly noteworthy for its synthetic intractability and inexplicable biogenesis. Despite five decades of research, this alkaloid has remained an elusive target for chemical synthesis due to insurmountable issues of reactivity and selectivity associated with all previously explored strategies. We herein report the chemical synthesis of (+)-brevianamide A (seven steps, 7.2% overall yield, 750 mg scale), which involves a bioinspired cascade transformation of the linearly fused (−)-dehydrobrevianamide E into the topologically complex bridged-spiro-fused structure of (+)-brevianamide A.Despite five decades of research, the alkaloid (+)-brevianamide A has remained an elusive target for chemical synthesis. Now, it has been shown that the total synthesis of (+)-brevianamide A can be achieved in seven steps and 7.2% overall yield to give 750 mg of the target compound.

Enantioconvergent reactions are pre-eminent in contemporary asymmetric synthesis as they convert both enantiomers of a racemic starting material into a single enantioenriched product, thus avoiding the maximum 50% yield associated with resolutions. All currently known enantioconvergent processes necessitate the loss or partial loss of the racemic substrate’s stereochemical information, thus limiting the potential substrate scope to molecules that contain labile stereogenic units. Here we present an alternative approach to enantioconvergent reactions that can proceed with full retention of the racemic substrate’s configuration. This uniquely stereo-economic approach is possible if the two enantiomers of a racemic starting material are joined together to form one enantiomer of a non- meso product. Experimental validation of this concept is presented using two distinct strategies: (1) a direct asymmetric coupling approach, and (2) a multicomponent approach, which exhibits statistical amplification of enantiopurity. Thus, the established dogma that enantioconvergent reactions require substrates that contain labile stereogenic units is shown to be incorrect. Enantioconvergent reactions convert both enantiomers of a racemic starting material into a single enantioenriched product. All currently known enantioconvergent processes necessitate the loss or partial loss of the racemic substrate’s stereochemical information. Now, an alternative approach has been developed that proceeds with full retention of the racemic substrate’s configuration.

Chiral amines are important building blocks in the pharmaceutical, agrochemical and chemical industries. There is a drive to augment traditional transition metal catalysts with 'green' alternatives such as biocatalysts. Transaminase (TA) biocatalysts can be used in combination with 'smart' sacrificial amine donors to synthesise a variety of aliphatic and aromatic amines from the corresponding aldehydes and ketones. Despite their enormous potential, the unfavourable reaction equilibrium often limits the widespread application of TAs for industrial synthesis. Recently we disclosed a new biomimetic amine donor N-phenyl putrescine (NPP), which was inspired by the biosynthesis of the dipyrroloquinoline alkaloids. NPP was demonstrated to have good activity with a library of commercial and wild-type TAs (total 25 TAs). This work focused on exploring the use of NPP with the Johnson Matthey TA kit (17 biocatalysts; eight S-selective and nine R-selective) and three different amine acceptors (vanillin, benzaldehyde and acetophenone). NPP worked well with all 17 TAs and gave the corresponding amine products vanillylamine, benzylamine and methylbenzylamine (MBA) in up to 85% high-performance liquid chromatography (HPLC) yield. From the screen, STA-14 was identified as a good biocatalyst for further analysis and used in a comparative screen of NPP versus the commonly used donor iPrNH2. It was found that NPP was the best amine donor and used to prepare S-methylbenzylamine in >99.5% enantiomeric excess (e.e.). This work, combined with our previous study, highlights the potential of NPP in the biocatalytic synthesis of amines.

Chiral amines are important building blocks in the pharmaceutical, agrochemical and chemical industries. There is a drive to augment traditional transition metal catalysts with ‘green’ alternatives such as biocatalysts. Transaminase (TA) biocatalysts can be used in combination with ‘smart’ sacrificial amine donors to synthesise a variety of aliphatic and aromatic amines from the corresponding aldehydes and ketones. Despite their enormous potential, the unfavourable reaction equilibrium often limits the widespread application of TAs for industrial synthesis. Recently we disclosed a new biomimetic amine donor N -phenyl putrescine (NPP), which was inspired by the biosynthesis of the dipyrroloquinoline alkaloids. NPP was demonstrated to have good activity with a library of commercial and wild-type TAs (total 25 TAs). This work focused on exploring the use of NPP with the Johnson Matthey TA kit (17 biocatalysts; eight S -selective and nine R -selective) and three different amine acceptors (vanillin, benzaldehyde and acetophenone). NPP worked well with all 17 TAs and gave the corresponding amine products vanillylamine, benzylamine and methylbenzylamine (MBA) in up to 85% high-performance liquid chromatography (HPLC) yield. From the screen, STA-14 was identified as a good biocatalyst for further analysis and used in a comparative screen of NPP versus the commonly used donor i PrNH2. It was found that NPP was the best amine donor and used to prepare S -methylbenzylamine in >99.5% enantiomeric excess (e.e.) This work, combined with our previous study, highlights the potential of NPP in the biocatalytic synthesis of amines.

Aim： Brucine （BRU） extracted from the seeds of Strychnos nux-vomica L is glycine receptor antagonist. We hypothesize that BRU may modify alcohol consumption by acting at glycine receptors, and evaluated the pharmacodynamic profiles and adverse effects of BRU in rat models of alcohol abuse. Methods： Alcohol-preferring Fawn-Hooded （FH/Wjd） rats were administered BRU （10, 20 or 30 mg/kg, sc）. The effects of BRU on alcohol consumption were examined in ethanol 2-bottle-choice drinking paradigm, ethanol/sucrose operant self-administration paradigm and 5-d ethanol deprivation test. In addition, open field test was used to assess the general locomotor activity of FH/Wjd rats, and conditioned place preference （CPP） was conducted to assess conditioned reinforcing effect. Results： In ethanol 2-bottle-choice drinking paradigm, treatment with BRU for 10 consecutive days dose-dependently decreased the ethanol intake associated with a compensatory increase of water intake, but unchanged the daily total fluid intake and body weight. In ethanol/sucrose operant self-administration paradigms, BRU （30 mg/kg） administered before each testing session significantly decreased the number of lever presses for ethanol and the ethanol intake, without affecting the number of sucrose （10%） responses, total sucrose intake, and the number of lever presses for water. Acute treatment with BRU （30 mg/kg） completely suppressed the deprivation-induced elevation of ethanol consumption. Treatment with BRU （10, 20, and 30 mg/kg） did not alter locomotion of FH/Wjd rats, nor did it produce place preference or aversion. Conclusion： BRU selectively decreases ethanol consumption with minimal adverse effects. Therefore, BRU may represent a new pharmacotherapy for alcoholism.

Land use and related pressures have reduced local terrestrial biodiversity, but it is unclear how the magnitude of change relates to the recently proposed planetary boundary (\"safe limit\"). We estimate that land use and related pressures have already reduced local biodiversity intactness–the average proportion of natural biodiversity remaining in local ecosystems–beyond its recently proposed planetary boundary across 58.1% of the world's land surface, where 71.4% of the human population live. Biodiversity intactness within most biomes (especially grassland biomes), most biodiversity hotspots, and even some wilderness areas is inferred to be beyond the boundary. Such widespread transgression of safe limits suggests that biodiversity loss, if unchecked, will undermine efforts toward long-term sustainable development.

Protected areas are widely considered essential for biodiversity conservation. However, few global studies have demonstrated that protection benefits a broad range of species. Here, using a new global biodiversity database with unprecedented geographic and taxonomic coverage, we compare four biodiversity measures at sites sampled in multiple land uses inside and outside protected areas. Globally, species richness is 10.6% higher and abundance 14.5% higher in samples taken inside protected areas compared with samples taken outside, but neither rarefaction-based richness nor endemicity differ significantly. Importantly, we show that the positive effects of protection are mostly attributable to differences in land use between protected and unprotected sites. Nonetheless, even within some human-dominated land uses, species richness and abundance are higher in protected sites. Our results reinforce the global importance of protected areas but suggest that protection does not consistently benefit species with small ranges or increase the variety of ecological niches. Protected areas are thought essential for biodiversity conservation, but few studies confirm that protection benefits species. Here, Gray and Hill et al . analyse a global, taxonomically broad database to show that local species richness and abundance are higher inside protected areas than outside.