Abstract: An isomer, enantiomer, diastereoisomer or tautomer of a compound, represented by formula I: 1

Abstract: A compound of formula I: wherein R1 is hydrogen, methyl, ethyl, methoxy or methylthio; R2 and R3 each independently is hydrogen or C1-3 alkyl; R4 is hydrogen, lower alkyl, methoxy, ethoxy, or benzyloxy; R5 is lower alkyl, lower cycloalkyl, (CH2)mC(O)OR6 wherein m is the integer 1 or 2 and R6 is lower alkyl, phenyl optionally substituted with C(O)OR7 wherein R7 is lower alkyl or phenyl (lower alkyl); or R6 is Het or Het(lower alkyl; or R4 and R5 together with the nitrogen atom to which they are attached form a nitrogen containing ring optionally substituted with benzyloxycarbonyl or with phenyl optionally substituted among other group with C(O)OR7 wherein R7 is lower alkyl or (lower alkyl)phenyl; X is selected from the group consisting of O, S, SO, SO2, NR8, wherein R8 is H or lower alkyl; and Y is C1-10 non-cyclic or cyclic alkyl; [(CH2)0-1]-phenyl, said phenyl ring optionally substituted; Het or Het(lower alkyl); or when X is NR8, wherein R8 is lower alkyl and Y is lower alkyl or