1. Derivatives of cyclic amino acid of general formula (I)   wherein: X is O, S, S(O), S(O)2, or NR1 wherein R1 is hydrogen, straight or branched alkyl of from 1 to 6 carbon atoms, benzyl, -C(O)R2 wherein R2 is straight or branched alkyl of from 1 to 6 carbon atoms, benzyl, or phenyl, or -CO2R3 wherein R3 is straight or branched alkyl of from 1 to 6 carbon atoms, or benzyl wherein benzyl and phenyl groups can be unsubstituted or substituted by from 1 to 3 substituents each independently selected from halogen, trifluoromethyl, and nitro group; R is hydrogen or lower alkyl of from 1 to 4 carbon atoms, or pharmaceutically acceptable salts thereof 2. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is O. 3. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is S. 4. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is sulfinyl. 5. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is sulfonyl. 6. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is NR1, wherein R1 is hydrogen, straight or branched alkyl of from 1 to 6 carbon atoms, benzyl, -C(O)R2, wherein R2 is straight or branched alkyl of from 1 to 6 carbon atoms, benzyl, or phenyl, -CO2R3 wherein R3 is straight or branched alkyl of from 1 to 6 carbon atoms, or benzyl. 7. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is imino. 8. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is NR1 wherein R1 is straight or branched alkyl of from 1 to 6 carbon atoms or is benzyl. 9. Derivatives of cyclic amino acid of general formula (I) according to claim 1 wherein X is -C(O)R2 wherein R2 is straight or branched alkyl of from 1 to 6 carbon atoms, benzyl, or phenyl. 10. Derivatives of cyclic amino acid of general formula (I) according to claim 6 wherein R1 is -CO2R3 wherein R3 is straight or branched alkyl of from 1 to 6 carbon atoms or benzyl. 11. Derivatives of formula (I) according to claim 1 repesenting (4-aminomethyl-tetrahydro-pyran-4-yl)-acetic acid or (4-aminomethyl-tetrahydro thiopyran-4-yl)-acetic acid. 12. A pharmaceutical composition having means for treating epilepsy, cramps, pains, states of fear, panic and depression comprising a therapeutically effective amount of a compound according to claim 1 and a pharmaceutically acceptable carrier. 13. A method for treating epilepsy comprising administering a therapeutically effective amount of a compound according to claim 1 to a mammal in need of said treatment. 14. A method for treating depression comprising administering a therapeutically effective amount of a compound according to claim 1 to a mammal in need of said treatment. 15. A method for treating states of fear comprising administering a therapeutically effective amount of a compound according to claim 1 to a mammal in need of said treatment. 16. A method for treating panic comprising administering a therapeutically effective amount of a compound according to claim 1 to a mammal in need of said treatment. 17. A method for treating pain comprising administering a therapeutically effective amount of a compound according to claim 1 to a mammal in need of said treatment.