Method for the extraction of keratin from dead animal skins

A compound of the formula I

• and its corresponding alkali metal, alkaline earth metal, ammonium and phosphonium salts,
• where
• R1 and R4 are identical or different and are selected from hydrogen, C6-C14-aryl and C1-C12-alkyl, unsubstituted or substituted by one or more SH or OH groups,
• R2 and R3 are identical or different and are selected from hydrogen, C6-C14-aryl and C1-C12-alkyl, unsubstituted or substituted by one or more SH or OH groups,
• at least one radical R2 or R3 not being hydrogen
• or R1 and R4 not being hydrogen,
• and it being possible in each case for two vicinal radicals R1 to R4 together to be alkylene,
• R5 is selected from hydrogen, C1-C12-alkyl, H—C═O or C1-C4-alkyl-C═O,
• X1, X2, X3 and X4 are selected from OH, SH and NHR5, where,
• if R1 to R4 contain at least one sulfur atom, at least one radical X1 to X4 is SH,
• and, if R1 to R4 contain no sulfur atom, at least two radicals X1 to X4 are SH.

A process for the preparation of compounds of the formula I, wherein

• (a) in a first stage, a diene of the formula II
• is reacted in the presence of a catalyst which is obtainable by bringing into contact
• at least one manganese compound, selected from A2Mn(Y1)4, AMn(Y1)3, MnY2, Mn(Y1)2 and Mn(Y1)3
• with at least one ligand L of the formula III
• where
• Y1 are identical or different and are selected from monovalent anions,
• Y2 is a divalent anion,
• A is selected from alkali metal and ammonium, which may be alkylated,
• R6 are identical or different and are selected from C1-C20-alkyl,
• and with at least one coligand which is derived from monocarboxylic acid, dibasic or polybasic carboxylic acids or diamines,
• with at least one peroxide to give the bisepoxide,
• (b) which is reacted in the presence of at least one basic catalyst with at least one nucleophile.