Justiciosides E–G, triterpenoidal glycosides with an unusual skeleton from Justicia betonica

Computational and Synthetic Investigation of Cationic Rearrangement in the Putative Biosynthesis of Justicane Triterpenoids

“…[2b] Decades of research have established that the biosyntheses of these pentacyclic triterpenoids occur via polyolefin cyclization of 2,3-oxidosqualene and subsequent cationic rearrangements of the D and E rings. [4–6] In contrast, the pathways that reorganize the A and B rings of pentacyclic triterpenoids, as represented by the justicanes (Figure 1), [7] are not clearly understood. Herein we report a synthetic, kinetic, and computational evaluation of the interconversion of the oleane skeleton to that of the justicane class (i.e.…”

“…[7] To resolve this ambiguity, we conducted NMR prediction calculations (Figure 1B). [13,14] Deviations from experimental data (in ppm) are shown for both assignments.…”

“…The spectral data for the material thus obtained are in excellent agreement with those reported for justicioside E aglycone ( 1 ). [7] …”

Saponins and a lignan derivative of Terminalia tropophylla from the Madagascar Dry Forest

“…The third sugar unit was identified as a glucoside as by its 1D TOCSY data [1D TOCSY: H-1‴ (selected): δ H 4.62, d, J = 8.0 Hz; H-2‴: δ H 3.16, t, J = 9.6 Hz; H-3‴: δ H 3.20, t, J = 9.6 Hz; H-4‴: δ H 3.30, t, J = 9.6 Hz; H-5‴: δ H 3.20, m; H-6‴: δ H 3.65 and 3.85, m]. The 13 C NMR chemical shifts of the sophorose moiety at the 28-position matched those of justicioside E (Kanchanapoom et al, 2005). Hence, the structure of compound 1 was determined as shown, and was named terminaliaside A ((3β,21β,22α)-3- O -(3′- O -angeloylpyranoglucosyl)-21,22-dihydroxy-28- O -sophorosyl-16-oxoolean-12-ene).…”

Computational and Synthetic Investigation of Cationic Rearrangement in the Putative Biosynthesis of Justicane Triterpenoids

“…[2b] Decades of research have established that the biosyntheses of these pentacyclic triterpenoids occur via polyolefin cyclization of 2,3-oxidosqualene and subsequent cationic rearrangements of the Da nd E rings. [4][5][6] In contrast, the pathways that reorganize the Aand Br ings of pentacyclic triterpenoids,a sr epresented by the justicanes (Figure 1), [7] are not clearly understood. Herein we report as ynthetic,k inetic, and computational evaluation of the interconversion of the oleane skeleton to that of the justicane class (i.e.…”