Intensified deracemization <i>via</i> rapid microwave-assisted temperature cycling

Cameli, Fabio; Xiouras, Christos; Stefanidis, Georgios D.

doi:10.1039/c8ce00575c

Cited by 43 publications

(47 citation statements)

References 28 publications

(4 reference statements)

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“…Simultaneous cooling and microwave heating improves reactor temperature control by preventing run away temperatures, ease post-synthesis vessel handling, modify the nucleation and growth of solid products [36][37][38][39] , and to explore non-thermal microwave effects 17,34,39 . Rapid adjustment to the optimal temperatures required during multistep syntheses is readily achieved in microwave-assisted reaction systems.…”

Section: Discussionmentioning

confidence: 99%

Microwave-assisted Automated Glycan Assembly

Flores¹,

Leichnitz²,

Sletten³

et al. 2021

Preprint

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Automated synthesis of DNA, RNA, and peptides provides quickly and reliably important tools for biomedical research. Automated glycan assembly (AGA) is significantly more challenging as highly branched carbohydrates require strict regio- and stereocontrol during synthesis. A new AGA synthesizer enables rapid temperature adjustment from -40 °C to +100 °C to control glycosylations at low temperature and accelerates capping, protecting group removal, and glycan modifications by using elevated temperatures. Thereby, the temporary protecting group portfolio is extended from two to four orthogonal groups that give rise to oligosaccharides with up to four branches. In addition, sulfated glycans and unprotected glycans can be prepared. The new design reduces the typical coupling cycles from 100 min to 60 min while expanding the range of accessible glycans. The instrument drastically shorten and generalizes the synthesis of carbohydrates for use in biomedical and material science.<br>

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Section: Discussionmentioning

confidence: 99%

Microwave-assisted Automated Glycan Assembly

Flores¹,

Leichnitz²,

Sletten³

et al. 2021

Preprint

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“…Existing literature addressing deracemization reveals no general agreement on the impact of various factors governing the shape of ee profiles during temperature cycling. While some results show an inflection point in the progress of ee with the number of temperature cycles [6,10,25,26], others show an exponential character throughout the evolution of the enantiomeric excess [8,9,21].…”

Section: Effect Of Initial Enantiomeric Excess Ee(0)and Particle Sizementioning

confidence: 98%

Complete chiral resolution in a continuous flow crystallizer with recycle stream

2021

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Repeated temperature cycling of crystals from a conglomerate forming chiral substance suspended in their saturated solution has shown to be effective in converting a mixture of both enantiomers into an enantiomerically pure state. While by now a large number of different setups has been demonstrated, here we show for the first time how a continuous flow temperature cycler with recycle stream is capable of establishing enantiopurity while converting a racemic starting suspension. By capturing the most significant parameters influencing the process kinetics a competitive productivity could be achieved. We show, that fast crystal dissolution at high undersaturations and fast crystal growth at high supersaturations are speeding up the process as long as nucleation can be kept to a minimum or avoided at all. Temperature cycling has shown to result in a shift towards larger sizes for the particle size distribution of the crystals suspended, which is detrimental to the present process governed by size-dependent solubility. By implementing an ultrasound unit recycled material was comminuted, resulting in nearly stable deracemization rates. Graphical abstract

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“…Under those circumstances, any energy flux passing through the suspension for long enough will lead to the disappearance of one population of homochiral crystals. A constant mechanical stress such as grinding (known as Viedma ripening) [22], numerous temperature cycles [23], long exposure to ultrasound [24], pressure stress [25] or microwaves [26] are general methods enabling the evolution of the initial dual population of particles to a single population of crystals containing a single enantiomer only, i.e., deracemization. Those methods operate rather close to thermodynamic equilibrium.…”

Section: Deracemization Induced By a Flux Of Energy Crossing The Susp...mentioning

confidence: 99%

Spontaneous and Controlled Macroscopic Chiral Symmetry Breaking by Means of Crystallization

Coquerel

Hoquante

2020

Symmetry

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In this paper, macroscopic chiral symmetry breaking refers to as the process in which a mixture of enantiomers departs from 50–50 symmetry to favor one chirality, resulting in either a scalemic mixture or a pure enantiomer. In this domain, crystallization offers various possibilities, from the classical Viedma ripening or Temperature Cycle-Induced Deracemization to the famous Kondepudi experiment and then to so-called Preferential Enrichment. These processes, together with some variants, will be depicted in terms of thermodynamic pathways, departure from equilibrium and operating conditions. Influential parameters on the final state will be reviewed as well as the impact of kinetics of the R ⇔ S equilibrium in solution on chiral symmetry breaking. How one can control the outcome of symmetry breaking is examined. Several open questions are detailed and different interpretations are discussed.

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Intensified deracemization via rapid microwave-assisted temperature cycling

Abstract: Rapid cooling and microwave heating substantially speed up temperature cycling-enhanced deracemization, while limiting the concomitant side reactions. During fast cooling, secondary nucleation is shown to enable deracemization.

Cited by 43 publications

References 28 publications

Microwave-assisted Automated Glycan Assembly

Microwave-assisted Automated Glycan Assembly

Complete chiral resolution in a continuous flow crystallizer with recycle stream

Spontaneous and Controlled Macroscopic Chiral Symmetry Breaking by Means of Crystallization

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