The invention relates to pharmaceutical chemistry notably to new biologically active substances (BAS) and their properties. In particular, the invention relates to Creatine derivatives having a general formula: NH═C(NH2)—N(CH3)—CH2—CO—NH—R*X, wherein R—amino acid residue of aliphatic, aromatic or heteroaromatic L-amino acid or its derivative representing a salts of amino acid, amino acid esters, amino acid amides or peptides; X—lower organic or mineral acid or water. New substances are prepared by interaction of aforesaid amides of sarcosine having a general formula of HN(CH3)—CH2—CO—NH—R*X, wherein: R is amino acid residue or substituted amino acid residue; X is low-molecular-weight organic acid or mineral acid or water, with a guanidinylating agents with the in organic solvents at temperature not exceeding 50° C. New chemical compounds can be used as a remedy possessing a neuroprotective activity.