The invention relates to α-oxygenated or α-thiolated carboxylic acid phenethylamide derivatives of the general formula I including the optical isomers thereof and mixtures of such isomers, wherein A stands for optionally substituted aryl or optionally substituted heteroaryl; X is oxygen or sulfur; Y is oxygen or sulfur; R1 is hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, haloalkyl, haloalkenyl, haloalkynyl or halocycloalkyl; R2 is hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkoxy-alkyl, alkoxy-alkenyl, alkoxy-alkynyl, whereof all alkyl- alkenyl-, alkynyl-, or cycloalkyl-groups me be optionally substituted by halogen; or optionally substituted arylalkyl, optionally substituted-aryl-alkenyl, optionally substituted aryl-alkynyl or optionally substituted aryloxy-alkyl; R3 is hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkyl-alkyl, alkoxy-alkyl, alkoxy-alkenyl, alkoxy-alkynyl, whereof all alkyl- alkenyl-, alkynyl-, or cycloalkyl-groups me be optionally substituted by halogen; or is optionally substituted aryl-alkyl, optionally substituted aryl-alkenyl, optionally substituted aryl-alkynyl, optionally substituted aryloxy-alkyl, optionally substituted heteroaryl-alkyl, optionally substituted heteroaryl-alkenyl or optionally substituted heteroaryl-alkynyl; R4 is alkyl, alkenyl, alkynyl, alkoxy-alkyl, alkoxy, alkenyloxy, alkynyloxy, alkylthio, alkanoyl, alkylamino, dialkylamino, alkoxycarbonyl, whereof all alkyl- alkenyl or alkynyl-groups me be optionally substituted by halogen; or is halogen, cyano, nitro, amino, formyl or carboxyl; R5 is hydrogen, alkyl, alkenyl or alkynyl; n is an integer 0, 1, 2, 3, or 4; B1 represents a bridge member —(CR10R11)q— or —(CHR10R11)r—Z—(CR12R13)8, wherein q is an integer 2, 3 or 4; r is an integer 0, 1; 2, 3; s is an integer 1, 2 or 3, provided that (r+s) is either 1, 2 or 3; Z is —O—, —S—, —SO— —SO2—, NR6—, —CO—, —OOC—, —COO, —NR6—CO—or —CO—NR6—; R6 is hydrogen or alkyl; R10, R11, R12 and R13 independently of each other are hydrogen or alkyl; and B2 is an alkylene bridge. These compounds possess useful plant protecting properties and may advantageously be employed in agricultural practice for controlling or preventing the infestation of plants by phytopathogenic microorganisms, especially fungi.