A novel continuous crystallizer design is described with the potential to provide improved control of crystal properties, improved process reproducibility, and reduced scale-up risk. Liquid and gas are introduced into one end of the tube at flow rates selected to spontaneously generate alternating slugs of liquid and gas that remain stable while cooling crystallization occurs in each liquid slug. Mixing within each stable self-circulating slug is maximized by controlling the slug aspect ratio through specification of liquid and gas flow rates. The crystallizer is designed so that nucleation and growth processes are decoupled to enhance the individual control of each phenomenon. Coaxial or radial mixers combine liquid streams to generate seed crystals immediately upstream of the growth zone where nucleation is minimized, and crystal growth is controlled by the varying temperature profile along the length of the tube. The slug-flow crystallizer design is experimentally demonstrated to generate large uniform crystals of L-asparagine monohydrate in less than 5 min.

Continuous-flow solution crystallization is an approach to manufacture pharmaceutical crystals with improved control of product characteristics, simplified post-crystallization operations, higher production rate flexibility, and reduced capital costs and footprint. An indirect ultrasonication-assisted nucleation process is designed to vary seed generation rate during operation independent of mass flow rate, by varying the ultrasonication power. The ultrasonication probe is pressed against a tube to generate a spatially localized zone within the tube inside of a temperature bath for the generation of crystal nuclei without heating or contaminating the supersaturated solution. This nucleation design is integrated into a continuous slug-flow crystallization process to generate uniform-sized product crystals within each slug at a high supersaturation level and a short residence time of ~8.5 min, without inducing significant secondary nucleation. By increasing size uniformity, the indirect ultrasonication-assisted slug-flow crystallizer has potential as a final crystallization step to produce crystals for direct compression tableting without having any possibility of metal contamination.

Sanglifehrin A (SFA) is a novel immunosuppressive natural product isolated from Streptomyces sp. A92-308110. SFA has a very strong affinity for cyclophilin A (IC(50) = 6.9 +/- 0.9 nM) but is structurally different from cyclosporin A (CsA) and exerts its immunosuppressive activity via a novel mechanism. SFA has a complex molecular structure consisting of a 22-membered macrocycle, bearing in position 23 a nine-carbon tether terminated by a highly substituted spirobicyclic moiety. Selective oxidative cleavage of the C(26)=C(27) exocyclic double bond affords the spirolactam containing fragment 1 and macrolide 2. The affinity of 2 for cyclophilin (IC(50) = 29 +/- 2.1 nM) is essentially identical to SFA, which indicates that the interaction between SFA and cyclophilin A is mediated exclusively by the macrocyclic portion of the molecule. This observation was confirmed by the X-ray crystal structure resolved at 2.1 A of cyclophilin A complexed to macrolide 16, a close analogue of 2. The X-ray crystal structure showed that macrolide 16 binds to the same deep hydrophobic pocket of cyclophilin A as CsA. Additional valuable details of the structure-activity relationship were obtained by two different chemical approaches: (1) degradation work on macrolide 2 or (2) synthesis of a library of macrolide analogues using the ring-closing metathesis reaction as the key step. Altogether, it appears that the complex macrocyclic fragment of SFA is a highly optimized combination of multiple functionalities including an (E,E)-diene, a short polypropionate fragment, and an unusual tripeptide unit, which together provide an extremely strong affinity for cyclophilin A.

Highly functionalized cyclopropanes can be produced with excellent enantioselectivity through an amine‐catalyzed organocatalytic cyclopropanation process (see scheme). Catalytically generated asymmetric ammonium ylides mediate the reaction, and the cyclopropane products can be produced as either enantiomer by using quinine‐ or quinidine‐derived catalysts.

A catalytic ammonium ylide based cyclopropanation process forms trans‐disubstituted cyclopropanes in good yield upon reaction with electron‐deficient alkenes (see scheme; EWG=electron‐withdrawing group). The reaction is also highly enantioselective when a stoichiometric amount of a chiral tertiary amine is used.

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A revised crystallization process for TAK-117, a selective PI3Kα inhibitor currently in Phase 1b clinical trials, was developed that greatly improved the overall purity, recovery, and physiochemical and bulk powder properties of the isolated product. The original process afforded material that was prone to agglomeration during drying, resulting in significant product losses during sieving as well as issues with drug product manufacturability. Opportunities to explore a wide array of possible crystallization routes and solvent options were limited because TAK-117 is only sparingly soluble in most commonly used organic solvents apart from dimethyl sulfoxide (DMSO) and acidic systems. However, reasonable productivities were achieved using DMSO at elevated temperatures (100 °C), and the optimized process leveraged thermal cycling to improve the aspect ratio of the isolated crystals, minimize agglomeration during drying, and improve the powder’s bulk properties. The revised process was found to produce material of acceptable quality across a total of six batches at 15 and 30 kg scales.

The total syntheses of 2,2'-epi-cytoskyrin A, rugulosin, and the alleged structure of rugulin are described. These naturally occurring bisanthraquinones and their relatives are characterized by novel molecular architectures at the core, at which lies a more or less complete, cage-like structural motif termed "skyrane". The strategies developed for their total synthesis feature a cascade sequence called the "cytoskyrin cascade" and deliver these molecules in short order and in a stereoselective manner.