| http://www.w3.org/ns/prov#value | - The present invention provides a compound having the structure: ##STR13## wherein each of R1, R2, R3, or R4 is independently hydrogen, or a lower alkyl; or wherein one but only one of R1, R2 or R3 is a lower alkyl azide group, a lower alkyl amine, a group comprising a lower alkyl group linked to a lower alkyl caboxylic acid or derivative, with each of the remaining two of R1, R2, or R3 is independ
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