A convenient synthesis of novel thiazolidin-4-one-linked pseudodisaccharides by tandem Staudinger/aza-Wittig/cyclization and their biological evaluation

A DFT study of NHC-catalyzed reactions of [3+3] annulations of 2-bromoenals and thioamides: mechanisms and regio- and stereoselectivities

“…DFT (M06-2X) calculations have been employed to investigate the possible mechanisms and origins of regio-and stereoselectivities of NHC-catalyzed [3+3] annulations of 2-bromoenals and thioamides. The most preferred mechanism for generating 1,3-thiazin-4-ones includes the following steps: (1) nucleophilic attack of the NHC on 2-bromoenal, (2) acetic acid-assisted proton transfer, (3) Br À anion release, (4) bicarbonate-assisted proton transfer, (5) thia-Michael addition, (6) 1,5-proton migration, (7) ring closure and (8) catalyst elimination. The ring closure step is rate-determining.…”

“…[1][2][3] 1,3-Thiazin-4-ones also have applications in organic syntheses and transformations. [4][5][6] Many methods have been developed to synthesize 1,3-thiazin-4-ones, [7][8][9][10] but the drawbacks, such as multiple steps and poor atom economy, have encouraged chemists to find simple, efficient and environmentally friendly synthetic routes.…”

One‐Pot Oxidation–Hydrocyanation Sequence Coupled to Lipase‐Catalyzed Diastereoresolution in the Chemoenzymatic Synthesis of Sugar Cyanohydrin Esters

“…Lipase PS-D and PS-C II preparations (Burkholderia cepacia lipase immobilized on diatomaceous earth and ceramic, respectively) were effective with the galactoside substrate but displayed very low or no activity toward the other sugar acetates ( Table 1, entries 1 and 2). Lipases A (CAL-A adsorbed on Celite) and B (CAL-B as a commercial Novozym 435 catalyst) from Candida antarctica and Candida rugosa lipase (CRL, adsorbed on Celite) gave generally low product yields for 1a-c (Table 1, entries [3][4][5]. Thermomyces lanuginosus lipase (Lipozyme TL IM) allowed highly efficient deprotection irrespective of which sugar was used ( Table 1, entry 6), although the reaction was not perfectly selective for C-6, particularly with substrate 1c.…”

“…[1] When such modifications are required to generate new asymmetric centers, high stereochemical control, in addition to the control caused by the stereostructure of the carbohydrate itself, is necessary. Examples of such reactions include a Staudinger reaction initiated process, [3] reductive amination, [4] Diels-Alder reaction, [5] and Grignard reaction. On the other hand, the C-6 position of aldohexoses is attractive for structural modifications that allow specific interactions with external substrates.…”

Synthesis of C-Pseudonucleosides Bearing Thiazolidin-4-one as a Novel Potential Immunostimulating Agent

“…14,15 The thiazolidin-4-one ring is a core substructure in various synthetic pharmaceuticals which are associated with diverse biological activities, 16 such as anticancer, antiviral, and antiinflammatory, and some thiazolidine derivatives; for instance, levamisole, pidotimod, and CGP52608 (Figure 1C) 17 exhibited strong immunostimulating activities. More recently, we have found that the thiazolidin-4-one linked pseudodisaccharides (Figure 1E) showed very good immunostimulatng activity, 18 which prompted us to develop the novel C-pseudonucleosides having a thiazolidin-4-one moiety for investigating their immune activity. Herein, as the continuation of our studies on functionalized nucleoside analogues, 19 we would like to report a simple and convenient synthesis of novel C-pseudonucleosides bearing thiazolidin-4-one (4 and 5) by one-pot, three-component condensation from the unprotected sugar aldehyde 1 (Scheme 1), and their biological effects on T cells, B cells, and the cytokine secretion of IL-2, IL-4, and IFN-γ from mouse splenocytes.…”