A solid-phase synthetic method for 3,4-dihydro-1H-2,1-benzothiazin-4-one 2,2-dioxide derivatives

Biomimetic and bioinspired molecular electrets. How to make them and why does the established peptide chemistry not always work?

“Biomimetic” and “bioinspired” define different aspects of the impacts that biology exerts on science and engineering. Biomimicking improves the understanding of how living systems work, and builds tools for bioinspired endeavors. Biological inspiration takes ideas from biology and implements them in unorthodox manners, exceeding what nature offers. Molecular electrets, i.e. systems with ordered electric dipoles, are key for advancing charge-transfer (CT) science and engineering. Protein helices and their biomimetic analogues, based on synthetic polypeptides, are the best-known molecular electrets. The inability of native polypeptide backbones to efficiently mediate long-range CT, however, limits their utility. Bioinspired molecular electrets based on anthranilamides can overcome the limitations of their biological and biomimetic counterparts. Polypeptide helices are easy to synthesize using established automated protocols. These protocols, however, fail to produce even short anthranilamide oligomers. For making anthranilamides, the residues are introduced as their nitrobenzoic-acid derivatives, and the oligomers are built from their C- to their N-termini via amide-coupling and nitro-reduction steps. The stringent requirements for these reduction and coupling steps pose non-trivial challenges, such as high selectivity, quantitative yields, and fast completion under mild conditions. Addressing these challenges will provide access to bioinspired molecular electrets essential for organic electronics and energy conversion.

Traceless Solid-Phase Organic Synthesis

Traceless solid-phase synthesis represents an ultimate sophisticated synthetic strategy on insoluble supports. Compounds synthesized on solid supports can be released without a trace of the linker that was used to tether the intermediates during the synthesis. Thus, the target products are composed only of the components (atoms, functional groups) inherent to the target core structure. A wide variety of synthetic strategies have been developed to prepare products in a traceless manner, and this review is dedicated to all aspects of traceless solid-phase organic synthesis. Importantly, the synthesis does not need to be carried out on a linker designed for traceless synthesis; most of the synthetic approaches described herein were developed using standard, commercially available linkers (originally devised for solid-phase peptide synthesis). The type of structure prepared in a traceless fashion is not restricted. The individual synthetic approaches are divided into eight sections, each devoted to a different methodology for traceless synthesis. Each section consists of a brief outline of the synthetic strategy followed by a description of individual reported syntheses.

A Facile Method for the Synthesis of Betrixaban

A facile method for the synthesis of N-(5-chloropyridin-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxybenzamide (Betrixaban) from 5-methoxy-2-nitrobenzoic acid is achieved by reduction, acylation, chlorination, acylation and the formation of the amidine. A dechlorinated impurity is avoided in this method. Using tetrahydrofuran as the solvent in the four steps makes its recovery easier. The total yield of the target compound is about 40% and this method is suitable for large-scale production.

Solid-phase synthesis of novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives via cyclization reactions of dithiocarboxy resin bound pyrazoles

A general method is described for the solid-phase synthesis of novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives. The sequence developed for this purpose is based on cyclization reactions of resin-bound 3,4-functionalized-5-amino-1-dithiocarboxypyrazoles 4 and 5, promoted by reaction with various isocyanates. The resin-bound pyrazoles produced by cyclization reactions of cyanocarboimidates 8 or 3-ethoxyacrylonitriles 9 with Merrifield resin linked hydrazine dithiocarbazate 3, serve as key intermediates for subsequent bicyclic heterocycle diversification. Reactions of the resin-bound 5-amino-1-dithiocarboxy pyrazoles 4 and 5 with various aryl isocyanates produce the novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives 6 and 7 in good yields and high purities.

Solid-phase synthesis of 1,3,6-trisubstituted-1H-thiazolo[4,5-c][1,2]thiazin-4(3H)one-2,2-dioxide derivatives using traceless linker

A new solid-phase route for preparation of 1,3,6-trisubstituted-1H-thiazolo[4,5-c][1,2]thiazin-4(3H)one-2,2-dioxide derivatives is described. Our synthetic route is begun with a thiazole resin and relies on the sulfonamide formation, Mitsunobu-type N-alkylation, cyclization, and nucleophilic substitution methodology cleavage on a solid support. The strategy permits the incorporation of three points of diversity into the thiazolo[4,5-c][1,2]thiazine ring system in good overall yields.