Yoshihiko Omura

Regioselective Mannich reaction of phenolic compounds and its application to the synthesis of new chitosan derivatives

Abstract A regioselective aminomethylation of 2,4-dihydroxybenzoyl compounds at the C(3) position was accomplished through a Mannich reaction of phenolic substrates with formaldehyde and secondary amines in methanol, whereas the reaction with primary amines included a subsequent cyclization step to yield the 1,3-benzoxazine derivatives. This sequence was successfully applied to the one-pot introduction of N -benzyl side chains to chitosan, a natural polyaminosaccharide, to afford a new chitosan derivative with improved solubility in an organic solvent.

Protective Effect of Chitin Urocanate Nanofibers against Ultraviolet Radiation

Urocanic acid is a major ultraviolet (UV)-absorbing chromophore. Chitins are highly crystalline structures that are found predominantly in crustacean shells. Alpha-chitin consists of microfibers that contain nanofibrils embedded in a protein matrix. Acid hydrolysis is a common method used to prepare chitin nanofibrils (NFs). We typically obtain NFs by hydrolyzing chitin with acetic acid. However, in the present study, we used urocanic acid to prepare urocanic acid chitin NFs (UNFs) and examined its protective effect against UVB radiation. Hos: HR-1 mice coated with UNFs were UVB irradiated (302 nm, 150 mJ/cm2), and these mice showed markedly lower UVB radiation-induced cutaneous erythema than the control. Additionally, sunburn cells were rarely detected in the epidermis of UNFs-coated mice after UVB irradiation. Although the difference was not as significant as UNFs, the number of sunburn cells in mice treated with acetic acid chitin nanofibrils (ANFs) tended to be lower than in control mice. These results demonstrate that ANFs have a protective effect against UVB and suggest that the anti-inflammatory and antioxidant effects of NFs influence the protective effect of ANFs against UVB radiation. The combination of NFs with other substances that possess UV-protective effects, such as urocanic acid, may provide an enhanced protective effect against UVB radiation.