prov:value
| - In the formula (I), the lower alkyl groups represented by R1 through R5 include, for example, straight- or branched-chain alkyl groups having 1 to 6, preferably 1 to 4, carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tertbutyl, pentyl and hexyl.
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