Characteristics of 3,5-di-tert-butyl-1,2-benzoquinone, studied as a pyridoxal-mimicking substance, is given. Its rich reactions remind of the general reactivity of o-quinones. Attention is paid to the reactions with primary amino groups bonded to the primary, secondary and tertiary carbon as well as with secondary and tertiary amines. Bulky tert-butyl groups in positions 3 and 5 play an important role as they affect the reaction course in many cases. They generally hinder the reactions in position 4 causing the preference given to nucleophilic attacks in positions 1 and 6. Main consideration is given to oxidative deaminations of amino acids and peptides.