Cyclo(L-phenylalanyl-trans-4-hydroxy-L-proline)

The title compound, C12H16Cl4, is a derivative of the natural product 1-isopropyl-4-methyl-cyclo-hexa-1,4-diene, and represents a diastereomer with two trans-fused cyclo-propane rings. Both enanti-omers are present in the non-centrosymmetric polar space group Pna21. The central cyclo-hexane ring is planar within 0.02 (1) Å. The C atoms of di-chloro-methyl-ene groups deviate from this plane by 1.19 (1) and -1.26 (1) Å, whereas the isopropyl and methyl groups are oriented more equatorially, deviating by 0.71 (1) and -0.87 (1) Å, respectively.

The title compound, C30H32N4, was synthesized by the photodimerization of trans-4-{2-[4-(di-methyl-amino)-phen-yl]ethen-yl}pyridine in benzene upon irradiation with UV light. This photodimer has a puckered cyclo-butane ring with the four aryl substituents in an r-1,t-2,c-3,t conformation. The puckering angle of the cyclo-butane ring is 32.22 (7)°, which is the largest among reported tetra-aryl-substituted cyclo-butanes. In the crystal, the mol-ecules form a hollow, one-dimensional structure extending parallel to the c axis via two different pairs of C-H⋯π inter-actions.

Fungal spoilage led to a considerable economic loss of foodstuff which ultimately affects public health due to mycotoxins production. Moreover, the consumption of commercial antifungal drugs creates side effects and develops antifungal resistance. To overcome these challenges, the current work was aimed to investigate novel antifungal cyclic dipeptide (CDP) from Lactobacillus coryniformis (Loigolactobacillus coryniformis) BCH-4. CDPs have flexible, cyclic, and stable conformation. The proline-based CDPs provide additional structural compatibility and bio-functional values. Keeping in view, high-performance liquid chromatography (HPLC) was performed to explore cyclo(L-Leu-L-Pro) from L. coryniformis BCH-4. The HPLC detected concentration (135 ± 7.07 mg/mL) exhibited in vitro antifungal activity of 5.66 ± 0.57 mm (inhibitory zone) against Aspergillus flavus. Based on these results, cyclo(L-Leu-L-Pro) was used as a bioprotectant for selected food samples (grapes, lemon, cashew nuts, and almonds). A significant impact of cyclo(L-Leu-L-Pro) was observed in contrast with MRS broth (control) and cell-free supernatant. In silico molecular docking analysis of this CDP was carried out against FAD glucose dehydrogenase, dihydrofolate reductase, and urate oxidase of A. flavus as target proteins. Among these proteins, FAD glucose dehydrogenase exerted strong interactions with cyclo(L-Leu-L-Pro) having S-score of - 8.21. The results evaluated that the detected CDP has strong interactions with selected proteins, causing excellent growth inhibition of A. flavus. Therefore, cyclo(L-Leu-L-Pro) could be used as a potent bioprotectant against food-borne pathogenic fungi.