then R3 and R4 (or R1 and R2) are other than H or alkyl substituted with hydroxyl, halogen, cyano or C1-C4 alkoxy; or 2) R2 is unsubstituted alkyl or unsubstituted cycloalkyl and R3 and R4 (or R1 and R2) are the same or different and are independently H or alkyl substituted with hydroxyl, halogen, cyano or C1-C4 alkoxy,