FIELD: organic chemistry, amino acids, pharmacy. SUBSTANCE: invention describes novel compounds of the formula (I) 
where B and D mean hydrogen atom independently each of other and Ar means (C1-C6)-alkyl with linear or branched chain; R1 is (C1-C6)-alkyl with linear or branched chain or Ar is substituted (C1-C6)-alkyl with linear or branched chain; J means (C1-C6)-alkyl with linear or branched chain; K means (C1-C6)-alkyl with linear or branched chain, phenyl-substituted (C1-C6)-alkyl with linear or branched chain where phenyl can be substituted with halogen atom; X means phenyl substituted with O-(C1-C6); Ar means phenyl or Ar is heterocyclic aromatic group taken among the group including: 2-pyridyl, 3-pyridyl, 4-pyridyl and imidazolyl group being Ar can be substituted with halogen atom that can be used for suppression of multidrug resistance. Invention describes also method of their synthesis, pharmaceutical composition and method of suppression of multidrug resistance. EFFECT: improved method of synthesis, valuable pharmacological properties. 11 cl, 3 tbl, 25 ex
