A compound of formula I: wherein R 1 is chloro, fluoro, bromo, methyl, ethyl, n-propyl, isopropyl, ethenyl, n-propenyl, isopropenyl, ethynyl, n-propynyl, isopropynyl, hydroxyl, methoxy, ethyoxy, n-propoxy, isopropoxy, tert-butyldimethylsilyloxy, phenyl, 4-methyl-phenyl, 4-methoxy-phenyl, 4-hydroxyphenyl, 4-cyano-phenyl, or 1,3-dioxoisoindolin-2-yl, R 2 is, each independently, hydrogen, halogen, hydroxyl; C 1-12 alkyl, C 1-12 alkoxy wherein these substituents are optionally substituted with halogen, R 3 is hydrogen; C 1-12 alkyl, C 3-10 cycloalkyl wherein these substituents are optionally substituted with halogen or oxo; C 1-12 alkyl-sulfonyl, aryl-sulfonyl; N-protecting group; aryl, heteroaryl wherein these substituents are optionally substituted with alkyl, alkoxy, halogen, or hydroxyl; R 4 and R 5 are each independently hydrogen, C 1-12 alkyl, C 2-12 alkenyl, C 2-12 alkynyl, C 1-12 alkoxy, hydroxyl optionally protected with a protective group selected from the group consisting of methoxymethyl, 2-methoxyethoxymethyl, tetrahydropyranyl, trimethylsilyl, tert-butyldimethylsilyl, tert-butyldimethylphenylsilyl and benzyl, or amino optionally protected with a protective group selected from the group consisting of tert-butoxycarbonyl, benzyloxycarbonyl, fluorenylmethoxycarbonyl and benzyl, -NR a R b, R 4 and R 5 taken together with the carbon atom to which they are attached, form carbonyl (C=O), oxime (C=NOR c), hydrazone (C=N-NR c R d), acetal (C(OR c)OR d), R c and R d, are each independently hydrogen, C 1-12 alkyl, C 2-12 alkenyl, C 2-12 alkynyl, N-protecting group, or O-protecting group; n is 0 to 12, m is 0 to 4, l is 2 to 8 wherein the N-protecting group is selected from the group consisting of tert-butoxycarbonyl, benzyloxycarbonyl, fluorenylmethoxycarbonyl and benzyl and the O-protecting group is selected from the group consisting of methoxymethyl, 2-methoxyethoxymethyl, tetrahydropyranyl, trimethylsilyl, tert-butyldimethylsilyl, tert-butyldimethylphenylsilyl, and benzyl, or racemate, enantiomer, diastereomer, mixture thereof, or pharmaceutically acceptable salt thereof, with the proviso that the following compounds are excluded: (2'R,6'S)-1-Methyl-6'-phenyl-5',6'-dihydrospiro[indoline-3,2'-pyran]-2,4'(3'H)-dione, and 6'-Hydroxy-3',4',5',6'-tetrahydrospiro[indoline-3,2'-pyran]-2-one. wherein R 1 is chloro, fluoro, bromo, methyl, ethyl, n-propyl, isopropyl, ethenyl, n-propenyl, isopropenyl, ethynyl, n-propynyl, isopropynyl, hydroxyl, methoxy, ethyoxy, n-propoxy, isopropoxy, tert-butyldimethylsilyloxy, phenyl, 4-methyl-phenyl, 4-methoxy-phenyl, 4-hydroxyphenyl, 4-cyano-phenyl, or 1,3-dioxoisoindolin-2-yl, R 2 is, each independently, hydrogen, halogen, hydroxyl; C 1-12 alkyl, C 1-12 alkoxy wherein these substituents are optionally substituted with halogen, R 3 is hydrogen; C 1-12 alkyl, C 3-10 cycloalkyl wherein these substituents are optionally substituted with halogen or oxo; C 1-12 alkyl-sulfonyl, aryl-sulfonyl; N-protecting group; aryl, heteroaryl wherein these substituents are optionally substituted with alkyl, alkoxy, halogen, or hydroxyl; R 4 and R 5 are each independently hydrogen, C 1-12 alkyl, C 2-12 alkenyl, C 2-12 alkynyl, C 1-12 alkoxy, hydroxyl optionally protected with a protective group selected from the group consisting of methoxymethyl, 2-methoxyethoxymethyl, tetrahydropyranyl, trimethylsilyl, tert-butyldimethylsilyl, tert-butyldimethylphenylsilyl and benzyl, or amino optionally protected with a protective group selected from the group consisting of tert-butoxycarbonyl, benzyloxycarbonyl, fluorenylmethoxycarbonyl and benzyl, -NR a R b, R 4 and R 5 taken together with the carbon atom to which they are attached, form carbonyl (C=O), oxime (C=NOR c), hydrazone (C=N-NR c R d), acetal (C(OR c)OR d), R c and R d, are each independently hydrogen, C 1-12 alkyl, C 2-12 alkenyl, C 2-12 alkynyl, N-protecting group, or O-protecting group; n is 0 to 12, m is 0 to 4, l is 2 to 8