The present invention relates to compounds of Formula, or an agronomically acceptable salt of said compounds wherein A1, A2, A3, X1, X2, R1, R2 and R4 are as defined herein. The system uses a file folder transmission unit at the sending end side to generate a directory structure file of the file folder. The two kinds of CM chitosan derived from shrimp’s and crab’s shells are powerful antioxidants to prevent lipid peroxidation of rat liver microsome.