Computational planning of the synthesis of complex natural products.

Training algorithms to computationally plan multistep organic syntheses has been a challenge for more than 50 years1-7. However, the field has progressed greatly since the development of early programs such as LHASA1,7, for which reaction choices at each step were made by human operators. Multiple software platforms6,8-14 are now capable of completely autonomous planning. But these programs 'think' only one step at a time and have so far been limited to relatively simple targets, the syntheses of which could arguably be designed by human chemists within minutes, without the help of a computer. Furthermore, no algorithm has yet been able to design plausible routes to complex natural products, for which much more far-sighted, multistep planning is necessary15,16 and closely related literature precedents cannot be relied on. Here we demonstrate that such computational synthesis planning is possible, provided that the program's knowledge of organic chemistry and data-based artificial intelligence routines are augmented with causal relationships17,18, allowing it to 'strategize' over multiple synthetic steps. Using a Turing-like test administered to synthesis experts, we show that the routes designed by such a program are largely indistinguishable from those designed by humans. We also successfully validated three computer-designed syntheses of natural products in the laboratory. Taken together, these results indicate that expert-level automated synthetic planning is feasible, pending continued improvements to the reaction knowledge base and further code optimization.

Laboratory analysis of organic acids, 2018 update: a technical standard of the American College of Medical Genetics and Genomics (ACMG).

Organic acid analysis detects accumulation of organic acids in urine and other body fluids and is a crucial first-tier laboratory test for a broad spectrum of inborn errors of metabolism. It is also frequently ordered as follow-up for a positive newborn screen result, as recommended by American College of Medical Genetics and Genomics newborn screening ACTion sheets and algorithms. The typical assay is performed by gas chromatography-mass spectrometry. These technical standards were developed to provide guidance for laboratory practices in organic acid analysis, interpretation, and reporting. In addition, new diagnostic biomarkers for recently discovered organic acidurias have been added.

Guidelines for radical reactions: some thirty years on.

In this viewpoint article we reflect on the state of play of organic free radical chemistry before the contributions of Beckwith et al. to our understanding of the factors that control intramolecular homolytic addition chemistry, and the rapid rise in the use of this chemistry once the impact of the "guidelines for radical reactions" became fully appreciated.

Flash chemistry: flow chemistry that cannot be done in batch.

Flash chemistry based on high-resolution reaction time control using flow microreactors enables chemical reactions that cannot be done in batch and serves as a powerful tool for laboratory synthesis of organic compounds and for production in chemical and pharmaceutical industries.

On inventing reactions for atom economy.

An important first step in making organic reactions more environmentally benign by design requires processes that are, to a first approximation, simple additions with anything else needed only catalytically. Since so few of the existing reactions are additions, synthesis of complex molecules requires the development of new atom-economic methodology. The prospect for such developments is probed in the context of ruthenium-catalyzed reactions. Using mechanistic reasoning, over 20 new processes of varying complexity have been designed and implemented. While some involved oxidation-reduction processes, most involved C-C bond-forming reactions.

Microwave-accelerated homogeneous catalysis in organic chemistry.

The efficiency of microwave flash heating in accelerating organic transformations (reaction times reduced from days and hours to minutes and seconds) has recently been proven in several different fields of organic chemistry. This specific account mainly summarizes our own experiences in developing rapid, robust, and selective microwave-assisted transition metal-catalyzed homogeneous reactions. Applications include selective Heck couplings, cross-couplings, and asymmetric substitutions. The science of green chemistry was developed to meet the increasing demand for environmentally benign chemical processes. We believe the combination of metal catalysis and microwave heating will be of importance in the search for green laboratory-scale synthesis.

Supercritical carbon dioxide as a green reaction medium for catalysis.

Carbon dioxide in its liquid or supercritical state (scCO(2)) has a prodigious potential as an environmentally benign reaction medium for sustainable chemical synthesis. Since the mid-1990s, rapidly increasing research efforts have shown that scCO(2) can replace conventional and potentially hazardous solvents in a wide range of processes. There is also increasing evidence that the application of scCO(2) can broaden the scope of catalytic synthetic methodologies. On the basis of the experience in our laboratories, this report analyzes the impact of scCO(2) on green organometallic catalysis.

H(2)O(2) in CO(2): sustainable production and green reactions.

Hydrogen peroxide is a "green" oxidant whose relatively high cost has prevented it from being applied to commodity chemical processing. Interestingly, those attributes of the current H(2)O(2) process that contribute to the high cost also contribute to its nonsustainable features. We have consequently explored the generation of hydrogen peroxide both by the AQ route and directly from hydrogen and oxygen using liquid CO(2) as the solvent, because CO(2) provides some unique advantages to H(2)O(2) synthesis.

A novel approach to high-throughput quality control of parallel synthesis libraries.

Combinatorial chemistry is a powerful tool to enhance drug discovery efforts in the pharmaceutical industry. One type of combinatorial chemistry, parallel synthesis, is now widely used to prepare numerous compounds of structural diversity. A novel high-throughput method for quality control of parallel synthesis libraries has been developed. The method uses flow injection MS, for proof of structure and estimation of purity, and a novel direct injection CLND technique for quantitation of amount. Following the synthesis of a small molecule library, compounds analyzed using this technique were characterized by mass spectrometry, and an accurate concentration of the compound was assessed by CLND. Characterization of one compound is completed in 60 s, allowing for up to 1000 compounds to be analyzed in a single day. The data is summarized using pass/fail criteria using internally developed software.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol.

Described herein is an efficient method for the synthesis of the eight positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-fucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative. Also reported for the acetates and the tri-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.