Liquid-phase RNA synthesis by using alkyl-chain-soluble support

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

Synthesizing organocatalysts is often a long and cost-intensive process, therefore, the recovery and reuse of the catalysts are particularly important to establish sustainable organocatalytic transformations. In this work, we demonstrate the synthesis, application, and recycling of a new lipophilic cinchona squaramide organocatalyst. The synthesized lipophilic organocatalyst was applied in Michael additions. The catalyst was utilized to promote the Michael addition of cyclohexyl Meldrum's acid to 4-chloro-trans-β-nitrostyrene (quantitative yield, up to 96% ee). Moreover, 1 mol % of the catalyst was feasible to conduct the gram-scale preparation of baclofen precursor (89% yield, 96% ee). Finally, thanks to the lipophilic character of the catalyst, it was easily recycled after the reaction by replacing the non-polar reaction solvent with a polar solvent, acetonitrile, with 91-100% efficiency, and the catalyst was reused in five reaction cycles without the loss of activity and selectivity.

From CPG to hybrid support: Review on the approaches in nucleic acids synthesis in various media

Solid-phase synthesis is, to date, the preferred method for the manufacture of oligonucleotides, in quantities ranging from a few micrograms for research purposes to several kilograms for therapeutic or commercial use. But for large-scale oligonucleotide manufacture, scaling up and hazardous waste production pose challenges that necessitate the investigation of alternate synthetic techniques. Despite the disadvantages of glass supports, using soluble supports as a substitute presents difficulties because of their high overall yield and complex purification steps. To address these challenges, various independent approaches have been developed; however, other problems such as insufficient cycle efficiency and synthesis of oligonucleotide chains of desired length continue to exist. In this study, we present a review of the current developments, advantages, and difficulties of recently reported alternatives to supports based on controlled pore glass, and discuss the importance of a support choice to resolve issues arising during oligonucleotide synthesis.

Uniform soluble support for the large-scale synthesis of sequence-defined macromolecules

A monodisperse soluble support is used as an effective tool for the large-scale, liquid-phase synthesis of sequence-defined macromolecules. This uniform support allows for direct characterisation and leads to a single peak in mass spectrometry.

Development of Kilogram-Scale Convergent Liquid-Phase Synthesis of Oligonucleotides

Oligonucleotide drugs show promise to treat diseases afflicting millions of people. To address the need to manufacture large quantities of oligonucleotide therapeutics, the novel convergent liquid-phase synthesis has been developed for an 18-mer oligonucleotide drug candidate. Fragments containing tetra- and pentamers were synthesized and assembled into the 18-mer without column chromatography, which had a similar impurity profile to material made by standard solid-phase oligonucleotide synthesis. Two of the fragments have been synthesized at ∼3 kg/batch sizes and four additional tetra- and pentamer fragments were synthesized at >300-g scale, and a 34-mer was assembled from the fragments. Critical impurities are controlled in the fragment syntheses to provide oligonucleotides of purities suitable for clinical use after applying standard full-length product purification process. Impurity control in the assembly steps demonstrated the potential to eliminate chromatography of full-length oligonucleotides, which should enhance scalability and reduce the environmental impact of the process. The convergent assembly and telescoping of reactions made the long synthesis (>60 reactions) practical by reducing production time, material loss, and chances for impurity generation.

Crystal structure of the Trypanosoma cruzi EIF4E5 translation factor homologue in complex with mRNA cap-4

Association of the initiation factor eIF4E with the mRNA cap structure is a key step for translation. Trypanosomatids present six eIF4E homologues, showing a low conservation and also differing significantly from the IF4Es of multicellular eukaryotes. On the mRNA side, while in most eukaryotes the mRNA contains cap-0 (7-methyl-GTP), the trypanosomatid mRNA features a cap-4, which is formed by a cap-0, followed by the AACU sequence containing 2′-O-ribose methylations and base methylations on nucleotides 1 and 4. The studies on eIF4E-cap-4 interaction have been hindered by the difficulty to synthesize this rather elaborated cap-4 sequence. To overcome this problem, we applied a liquid-phase oligonucleotide synthesis strategy and describe for the first time the crystal structure of a trypanosomatid eIF4E (T. cruzi EIF4E5) in complex with cap-4.

The TcEIF4E5-cap-4 structure allowed a detailed description of the binding mechanism, revealing the interaction mode for the AACU sequence, with the bases packed in a parallel stacking conformation and involved, together with the methyl groups, in hydrophobic contacts with the protein. This binding mechanism evidences a distinct cap interaction mode in comparison with previously described eIF4E structures and may account for the difference of TcEIF4E5-cap-4 dissociation constant in comparison with other eIF4E homologues.

Liquid-Phase Oligonucleotide Synthesis: Past, Present, and Future Predictions

Therapeutic oligonucleotides have emerged as a powerful paradigm with the ability to treat a wide range of the human diseases. As a result, we have witnessed more than one hundred oligonucleotides currently in active clinical trials and eight Food and Drug Administration (FDA)-approved drugs. Until now, the demand for oligonucleotide-based drugs has been fulfilled by conventional solid-phase synthesis in an effective manner. However, there are products in advanced stages of clinical trials projecting a collective demand of metric ton quantities in the near future. Therefore, large-scale manufacturing of these products has become a high priority for process chemists. This article summarizes the advances in liquid-phase oligonucleotide synthesis (LPOS) as a possible alternative strategy to meet the scale-up challenge. A review of the literature describing major efforts in developing LPOS technologies is presented. Gratifyingly, serious attempts are under way to develop an efficient environmentally benign green chemistry protocol that is scalable and cost effective for the manufacturing of oligonucleotides. A summary of the most innovative LPOS protocols has been included to provide a glimpse of what may be possible in the future for large-scale production of oligonucleotides. © 2019 by John Wiley & Sons, Inc.

Synthesis of oligonucleotides on a soluble support

Oligonucleotides are usually prepared in lab scale on a solid support with the aid of a fully automated synthesizer. Scaling up of the equipment has allowed industrial synthesis up to kilogram scale. In spite of this, solution-phase synthesis has received continuous interest, on one hand as a technique that could enable synthesis of even larger amounts and, on the other hand, as a gram scale laboratory synthesis without any special equipment. The synthesis on a soluble support has been regarded as an approach that could combine the advantageous features of both the solution and solid-phase syntheses. The critical step of this approach is the separation of the support-anchored oligonucleotide chain from the monomeric building block and other small molecular reagents and byproducts after each coupling, oxidation and deprotection step. The techniques applied so far include precipitation, extraction, chromatography and nanofiltration. As regards coupling, all conventional chemistries, viz. phosphoramidite, H-phosphonate and phosphotriester strategies, have been attempted. While P(III)-based phosphoramidite and H-phosphonate chemistries are almost exclusively used on a solid support, the "outdated" P(V)-based phosphotriester chemistry still offers one major advantage for the synthesis on a soluble support; the omission of the oxidation step simplifies the coupling cycle. Several of protocols developed for the soluble-supported synthesis allow the preparation of both DNA and RNA oligomers of limited length in gram scale without any special equipment, being evidently of interest for research groups that need oligonucleotides in large amounts for research purposes. However, none of them has really tested at such a scale that the feasibility of their industrial use could be critically judged.

Synthetic Method for Oligonucleotide Block by Using Alkyl-Chain-Soluble Support

A straightforward method for the synthesis of oligonucleotide blocks using a Cbz-type alkyl-chain-soluble support (Z-ACSS) attached to the 3'-OH group of 3'-terminal nucleosides was developed. The Z-ACSS allowed for the preparation of fully protected deoxyribo- and ribo-oligonucleotides without chromatographic purification and released dimer- to tetramer-size oligonucleotide blocks via hydrogenation using a Pd/C catalyst without significant loss or migration of protective groups such as 5'-end 4,4'-dimethoxtrityl, 2-cyanoethyl on internucleotide bonds, or 2'-TBS.