| http://www.w3.org/ns/prov#value | - Preferred embodiments of this invention are those compounds of formula I wherein n is 0 or 1, R1 is a phenyl or phenylalkyl, especially phenyl-C1 -C5 alkyl; R2 is hydrogen, ##STR21## wherein R7 is hydrogen or lower alkyl and R8 is lower alkyl, or R2 represents an alkali metal salt, such as lithium; R3 is aminoalkyl, such as amino-C2 -C5 -alkyl; X is L-proline, and R4 is hydrogen, or represents an
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