Antidiabetic 3,4,5-trihydroxypiperidines

DETAILED DESCRIPTION What is claimed is: 1.
A compound of the formula ##STR264## in which R.
sub.
1 is C.
sub.
5 -C.
sub.
30 alkyl, C.
sub.
2 -C.
sub.
18 alkenyl, C.
sub.
2 -C.
sub.
18 alkinyl, C.
sub.
3 -C.
sub.
8 cycloalkyl, C.
sub.
3 -C.
sub.
8 cycloalkenyl, C.
sub.
3 -C.
sub.
8 -cycloalkinyl, phenyl (a), C.
sub.
1 -C.
sub.
2 and C.
sub.
7 -C.
sub.
30 alkyl substituted by phenyl (b) or substituted C.
sub.
1 -C.
sub.
4 -alkyl said C.
sub.
5 -C.
sub.
30 alkyl, cycloalkyl, cycloalkenyl and cycloalkinyl being unsubstituted or substituted by hydroxy, C.
sub.
1 -C.
sub.
4 -alkoxy, acyloxy, amino, mono- C.
sub.
1 -C.
sub.
4 alkylamino, di-C.
sub.
1 -C.
sub.
4 alkylamino, acylamino, mercapto, C.
sub.
1 -C.
sub.
4 alkylthio, halogen, C.
sub.
1 -C.
sub.
4 alkylcarbonyl, carboxyl nitro, cyano, formyl, sulfo, a heterocyclic radical derived from a hexose or pentose, attached to the alkyl moiety directly via a ring atom or via an --O--, --S-- or --NH-bridge or naphthyl said phenyl (a) being unsubstituted or substituted by C.
sub.
1 to C.
sub.
10 alkyl, C.
sub.
1 to C.
sub.
10 chloroalkyl, C.
sub.
1 to C.
sub.
10 nitroalkyl, C.
sub.
1 to C.
sub.
10 cyanoalkyl, C.
sub.
1 to C.
sub.
10 alkenyl, hydroxyl, C.
sub.
1 to C.
sub.
4 alkoxy, amino, mono-C.
sub.
1 to C.
sub.
4 alkylamino, di-C.
sub.
1 -C.
sub.
4 alkylamino, mercapto, C.
sub.
1 -C.
sub.
4 alkylthio, carboxyl, C.
sub.
1 -C.
sub.
4 carbalkoxy, sulfo, C.
sub.
1 -C.
sub.
4 alkylsulfonyl, phenylsulfonyl, aminosulfonyl, C.
sub.
1 -C.
sub.
4 alkylaminosulfonyl, di-C.
sub.
1 -C.
sub.
4 alkylaminosulfonyl, nitro, cyano, formyl, C.
sub.
1 -C.
sub.
4 alkylcarbonylamino, C.
sub.
1 -C.
sub.
4 alkylcarbonyl, benzoyl, benzylcarbonyl or phenylethylcarbonyl; said substituted C.
sub.
1 -C.
sub.
4 alkyl being substituted by hydroxy, C.
sub.
1 -C.
sub.
4 -alkoxy, acyloxy, amino, mono- C.
sub.
1 -C.
sub.
4 alkylamino, di-C.
sub.
1 -C.
sub.
4 alkylamino, acylamino, mercapto, C.
sub.
1 -C.
sub.
4 alkylthio, halogen, C.
sub.
1 - C.
sub.
4 alkylcarbonyl, carboxyl nitro, cyano, formyl, sulfo, a heterocyclic radical derived from a hexose or pentose, attached to the alkyl moiety directly via a ring atom or via an --O--, --S-- or --NH--bridge or naphthyl, said acyl being derived from an aliphatic carboxylic acid having from 1 to 7 C-atoms, a phenyl carboxylic acid, unsubstituted or substituted by carboxy, hydroxy, halogen, C