ON THE STRUCTURES OF SCHISANLACTONE C AND SCHISANLACTONE D, TWO NEW TRITERPENE LACTONES FROM SCHISANDRA SP.

Two new triterpene lactones, schisanlactone C and D, besides chicanine, schisan- lactone A and B reported in the earlier papers. were isolated from the fruits of Schisandra sp. gathered in the District of Xiangfan, Hubei Province of China The structures 1a for schisanlactone C and 2a for schisanlactone D have been deduced on the basis of UV, IR. ~1H NMR, ~(13)C NMR spectra and CD curves. 1a, C_(30)H_(40)O_5, m. p. 257～258℃, [α]_D+377°(c 0.663, CHCl_3), λ_(max)(CH_3OH): 215(log e 4.12), 265(3. 84), 334(4.22)nm; v_(max): 3510(OH), 1720, 1690(lactone carbonyl- 26, and -3); m/z: 480.2862 (C_(30)H_(40)O_5 M~+), 462.2759 (C_(30)H_(38)O_4, M~+-H_2O), 422. 2457 (C_(27)H_(34)O_4),326.2213(C_(22)H_(30)O_2,the nuclear fragment of 17-C～20-C cleavage),283. 1692 (C_(19)H_(23)O_2), 231. 1385(C_(15)H_(19)O_2), 173.0964(C_(12)H_(13)O_2), 155. 0729(C_8H_(11)O_3, the side chain fragment of 17-C～20-C cleavage), 111. 0576(C_6H_7O_2, cleavage of 20-C～22-C; δ_H(400 MHz, CDCl_3): 6.68(1H, J_(1,2)=12.21, 1-H), 6.61 (1H, J_(23B,24)=6.10, J_(23A,24)=1. 53, J_(24,27)0.5, 24-H), 6.23(1H, s, 19-H). 5.81(1H, J_(1,2)=12.21, 2-H), 4.31(1H, J_(22,23A) =12. 82, J_(22,23B)=3. 66, 22-H), 2.49(1H, J_(5α,6β)=6. 10, J_(5α,6β)=12. 82, 5α-H), 1. 94 (3H, m, 27-H), 1.54, 1.41, 1. 32, 1.10, 0.92(each 3H, s, 29-H, 30-H, 21-H, 28-H, 18-H respectively); ~(13)C NMR data(100. 6MHz, see Table 1); CD curves(c 0. 06, MeOH) [θ](nm): 6400(228, tr), 25600(245, pk), 4800(275, tr), 48000(331, pk), 0(400). The only difference between schisanlactone C and schisanlactone A (1b) is the presence of a hydroxyl at 20-C indicated in ~1H NMR(absence of 20-H coupling with 21-H, and down field shift of 21-H), ~(13)C NMR(down field shift of 20-C to δ 75.40 and corresponding β, γ shifts), and MS(the fragments, C_8H_(11)O_3 and C_(22)H_(30)O_2, of 17- C～20-C cleavage). The absolute configurations, 22R and 20R, were determined by the positive Cotton effect at 245nm(n→π~*) in CD and the chemical shift differences, Δδ_(21-H)=-0. 28 and Δδ_(18-H)=-0.14, as compared to those found in withanolides. Schisanlactone D(2a), C_(30)H_(44)O_3, m.p. 257～259℃, [α] D+92.9°(c 0. 297 CHCl_3), λ_(max) (CH_3OH): 208(loge 3.93) nm; v_(max)(KBr): 1725, 1710(α, β-unsaturated δ-lactone, and saturated ketone), no hydroxyl peak; MS (see Fig 1); δ_H(400MHz, CDCl_3): 6. 61(1H, J_(23B,24)=6. 41, J_(23A,24)=1. 83, J_(24,27)0. 5, 24-H), 5. 30 (1H, J_(11,12A)=5. 80, J_(11,12B) 1. 5, J_(11,8)0. 5, 11-H), 4 . 48(1H, J_(20,22)=13.12, J_(22,23A)=3.36, J_(22,23B)=3. 66, 22-H), 2. 73(1H, J_(2a,2e)=15. 26, J_(2a,1a)=13. 43, J_(2a,1e)=6. 41, 2a-H), 2.40(1H, m, 12A-H), 2. 39(1H, m, 23A-H), 2. 20(1H, m, 20-H), 2. 12(1H, m,23B-H), 2.08(1H, m, 2e-H), 2. 05(1H, m, 12B-H), 1.92(3H, J_(23A,27)=1.22, J_(23B,27)0. 5, J_(24,27)0. 5, 27-H), 0. 99 (3H, J_(20,21)=6.41, 21-H), 1.24, 1.08, 1.07, 0.74, 0.72(each 3H, s, 29-H, 30-H, 19-H, 28-H, 18-H); ~(13)C NMR data(100.6MHz, see Table 1); CD curves (c 0.09, MeOH) [θ] (nm): 3013(237, tr), 6830(255, pk), -603(300, tr), 0(330). The ~1H NMR and ~(13)C NMR spectra mentioned above indicate that schisanlactone D possesses the same lactone side chain as that of 1b and schisanlactone B, and the same nucleus as that of schisanhenric acid(2b). Therefore, the structure of 2a has been assigned to schisanlactone D. Furthermore, the same fragments in high resolution mass spectra of 2a and 2b confirmed the above proposal(see Fig 1). Similar to the case of schisanlactone C 1, a positive Cotton effect at 255 nm(n→π~*) in CD measurement of schisanlactone D allowed the assignment of R configuration to 22-C.