| CPC C07C 67/44 (2013.01) [C07C 45/50 (2013.01); C07C 51/235 (2013.01)] | 10 Claims | 
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               1. A compound of following formula (I): 
              ![]() wherein: 
            R1, R2, R3 and R4 are each independently H or a (C1-C30) alkyl group, provided: 
                the total sum of the number of carbon atoms of R1, R2, R3 and R4 is equal to 6+4x, wherein x is an integer of 1 to 6; 
                  at most two among R1, R2, R3, and R4 are H; and 
                  at least one of groups R1, R2, R3, or R4 comprises or is a tert-butyl group; and 
                R5 is H, OR, or NR′R″, wherein R, R′ and R″, the same or different, are H or a (C1-C10) alkyl group. 
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