| abstract |
For preparing the novel bestatin compounds of the formula having R1 and R2 in accordance with the preceding Patent Claim 1, an alpha -hydroxybeta -amino acid of the formula is used as the starting material. The latter is condensed, optionally after having protected the functional groups which are not to participate in the subsequent reaction, with a beta -amino acid of the formula using a peptide-linking method. Protective groups which may optionally be present are subsequently removed. The optically pure diastereoisomers can be readily obtained from the compounds of the formula (III). The alpha -hydroxybeta -amino acids can be prepared by hydrolysing a corresponding cyanohydrin whose amino group is optionally protected. The novel compounds inhibit certain enzymes which decompose bleomycin and in this way amplify the anti-tumour activity of the bleomycins. |