We report a coupling reaction of thioamides and sulfonyl azides to generate sulfonyl amidines in the absence of any activation additives. The reaction progresses in various solvents under mild conditions. Water exhibits the highest performance with respect to efficiency.

Kersen (Muntingia calabura L) fruits have the potential to be used as an active ingredient in sunscreens because of phenolic and flavonoid content that can absorb UV rays. This study aims to determine the percentage of erythema/pigmentation transmission and SPF value as parameters for sunscreen activity.  Kersen fruits were extracted by maceration using 96% ethanol. The ethanol extract of Kersen Fruits was also fractionated to separate the components of the active compounds based on the polarity level using n-hexane, ethyl acetate, and ethanol as solvents. The test was carried out using the in vitro method by measuring the ability of the material to absorb ultraviolet light at a wavelength of 292.5-372.5 nm. This research was conducted at concentrations of 100, 200, 400, 600, and  800 µg/mL for ethanol, lyophilisate, n-hexane, and ethanol fractions, while the ethyl acetate fraction concentrations are 50, 100, 150, 200, 250 µg/mL. The results showed the best value at the ethyl acetate fraction concentration of 250 µg/mL with % Te of 5.28 and % Tp of 28.65 and the SPF value of 16.54. Based on the % Te and Tp, the ethyl acetate fraction exhibited protection against erythema and pigmentation with the category of extra protection and based on the SPF value with the category of ultra protection.

Click-type reaction has become increasingly important as the powerful approach of bio-orthogonal ligation method. 1 We recently reported a new class of click-type chemoselective reaction between thioamides and sulfonyl azides that furnishes sulfonyl amidines in the absence of any activation additives. 2 The reaction proceeds by mixing a thioamide and a sulfonyl azide at room temperature in various solvents. Increment of the solvent polarity enhances the reaction efficiency and water displayed the highest performance among solvents examined. These features of reaction well satisfy the prerequisite for the biological application. The solvent effect also suggests that the ionic resonance form of thioamides could be preferentially stabilized in polar protic solvents to accelerate the coupling reaction. In the previous report, we suggested an analogous mechanism to the coupling reaction of sulfonyl azides with thioacid derivatives (sulfo-click reaction), 3 in which ionic states mainly contribute to the mechanism. In this report, we disclose a non-concerted twostep pathway for the coupling reaction based on both of the experimental and computational investigation of the reaction efficiency by varying the substituents on the respective phenyl rings in thioacetanilide and benzenesulfonyl azide, which enabled to design a combination of thioamide and sulfonyl azide resulting the desired amidine very efficiently in a high yield. Scheme 1 shows possible two pathways for the coupling reaction in analogy to the proposed mechanism for the sulfo-click reaction 3b,c and 1,3-dipoler cycloadditions of organic azides and cyclic ketene derivatives. 4 Thioamide derivatives favorably transform to the resonance structures 5 T* that can react with electron-poor sulfonyl azides by an initial bond-formation

The public widely uses kersen (Muntingia calabura L) fruit for consumption and treatment because Kersen fruit has various vitamins, minerals, and secondary metabolite compounds that reduce free radicals. The purpose of this study was to see the effectiveness of kersen fruit as an antioxidant agent. In this study, the samples used were ethanol extract (EE), Aqueous ethanol fraction (EF), ethyl acetate fraction (EAF), and n-hexane (HF) fraction from kersen fruit (Muntingia calabura L). The samples were evaluated by observing the antioxidant activity profile using various methods, i.e., nitric oxide, β-carotene bleaching assay, hydroxyl radicals, and iron chelating. The results of this study showed that the IC50 values of EE (31.05 μg/mL), AEF (33.86 μg/mL), FEA (40.48 μg/ml) gave powerful antioxidant activity while HF showed weak results (459 μg/ml). In the nitric oxide method. The hydroxyl radical method with IC50 values of 32.06 μg/mL (EE), 38.73 μg/mL (EF), 22.18 μg/mL (EAF) gave very strong activity, and 53.37 μg/mL (HF) with strong activity. The β-carotene bleaching method gave powerful antioxidant activity results with IC50 values <50 μg/mL in each sample. The Iron Chelation method showed weak antioxidant activity (IC50 > 200 μg/mL) of each sample. Based on the results obtained, it can be concluded that the antioxidant activity of extracts and fractions in kersen fruit has a different activity profile according to the test method used.