4-dioxo-1,4-dihydronaphthalen-2-yl)methyl]-l-cysteine conjugates were obtained in good yields by acid-catalyzed condensation of substituted 2-hydroxy-1,4-naphthoquinones with N-acetyl-l-cysteine and paraformaldehyde. Based on this reaction, a first synthesis of fibrostatins B, C, and D was developed. A series of N-acetyl-S-[(3-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)methyl]-l-cysteine conjugates were