Abstract The novel natural product xyloallenoide A, isolated from the marine mangrove endophytic fungus from the South China Sea, and its diastereoisomer xyloallenoide A1, which contain N-methyl-substituted amino acids, were synthesized. The absolute configurations of the amino acid units of xyloallenoide A were finally confirmed to be L-Lys, Me-D-Val, and Me-L-Ala. This report represents a practical and attractive alternative for ...