6-one, 15) were isolated from red spice paprika (Capsicum nnnuum Vdr. longurn) and characterized by their UVjVIS, CD, 'Hand 13C-NMR, and mass spectra. Our investigations demonstrate that the configuration of the 3,5,6-trihydroxy-5,6-dihydro-&end group may differ depending on the biological source.
1. Introduction.
-Different varieties of paprika (Capsicum annuum) have been investigated for a long time. It has been established that capsanthin (1) and capsorubin (2), both containing the five-membered ring K-end group, are the most abundant carotenoids in these vegetables. Furthermore, many other carotenoids with interesting structures, especially those with the oxabicyclo-&end group and the 3,5,6-trihydroxy-5,6-dihydro-/?end group, have been isolated [1][2].
Naturally occurring carotenoids with the 3,5,6-trihydroxy-5,6-dihydro-j-end group have been isolated from different sources. Heteroxanthin (3) was isolated from Euglena gracilis [3], karpoxanthin (4) from ripe hips of Rosa pomifera [4], karpoxanthin (4) and 6-epikarpoxanthin (5) from petals and pollen of Lilium trigrinum [ 5 ] , latoxanthin (6) from petals of Rosa foetida [6], and neoflor (7) and 6-epineoflor (8) from petals of Trollius europaeus [7].
The structure elucidation of the 3,5,6-trihydroxy-5,6-dihydro-P-end group was performed by Eugster and co-workers [8] [9]. Several ionone derivatives and carotenoids bearing this end group were prepared by partial synthesis, and the spectroscopic data for the 3,5,6-trihydroxy-5,6-dihydro-P-end group with the (3S,5R,6R) (A), (3S,5S,6S) (B), (3S,5R,6S) (C), and (3S,5S,6R) (D) configuration have been established.
Based on these results, the configuration of the 3,5,6-trihydroxy-5,6-dihydro-P-end group was established as (3S,5R,6R) (A) in karpoxanthin ((3S,5R,6R)-4) originating from ripe hips of Rosa pomifera [4], in latoxanthin ((3S,5R,6R)-6) originating from Rosa foetida [6], and in neoflor ((3S,SR,6R)-7) originating from Trollius europaeus [7], and as (3S,5R,6S) (C) in 6-epikarpoxanthin ((3S,5R,6S)-5) originating from ripe hips of Rosa pomifera [4] and in 6-epineoflor ((3S,5R,6S)-8) originating from Trollius europaeus [7]. In contrast, it is of great interest that for karpoxanthin, isolated from red paprika, the (3S,SS,6S)-configuration (B), i.e., (3S,5S,6S,3'S)-4, was established.
During our investigations of different species of paprika (Capsicum annuum), some novel carotenoids with the 7-oxabicyclo[2.2. llheptyl-end group (3,6-epoxycyclohexyl)