Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class esters [acyl-XR, etc.; R'kE(=O)l(OH)m (l≠0; ≥1 (OH):=(XR)), etc.; X=O,S,Se,Te,etc.; R≠H]
                 aspartame
                 1 Class ortho esters [RC(OR')3 (R'≠H), C(OR')4 (R'≠H)]
                 2 Class lactones [~OC(=O)[CH2]n~] - cyclic esters of hydroxy carboxylic acids
                 3 Class lactides
                 4 Class glycerides
                 5 Class phosphoglycerides [RC(=O)OCH2CH(OC(=O)R)CH2OP(=O)(OR)2]