δ H | Multiplicity | Isomer | Assignment |
---|---|---|---|
5.52 | d | β-1 | H1′ |
5.18 | d | α-4 | H1′ |
5.11 | m | α-3 | H1′ + H3′ |
4.95 | d | β-3 | H3′ |
4.66 | m | α/β-2 | H2′ |
4.09 | d | β-4 | H5′ |
1.59 | d | α-1 | −CH3 |
1.42 | d | S-Naproxen | −CH3 |
Chemical shifts are referenced to acetonitrile at δ 2.0. Glucuronide ring protons are numbered according to Fig. 1. The signal at δ 5.11 for the α-3-O-acyl isomer is a superposition of the H1′ and H3′ protons; thus, the integrated signals are divided by 2 prior to kinetic analysis to get the signal corresponding to one proton. The CH3 group used for quantitation of the α-1-O-acyl isomer andS-naproxen aglycone is the α-methyl group in the acetic acid moiety of S-naproxen. This signal is divided by 3 prior to kinetic analysis to get the signal corresponding to one proton. For the β-1-O-acyl glucuronide and the α/β-2-, α/β-3-, and α/β-4-O-acyl isomers this methyl group appears as an unresolved band in the region δ 1.51 to 1.53 and cannot be used for quantitation.
d, doublet; m, multiplet.