Supplementary information
Spectral data of the isolated compounds
Compound1: Cyclo(D-Pro-D-Leu), (3R,8aR)-3-(2-methylpropyl)hexahydropyrrolo[1,2a]pyrazine-1,4-dione: was obtained as white amorphous powder; Melting point: 156.59 ºC;
[a]D -89 (c, 0.02, MeOH); UV max : 210 nm (MeOH); 1H NMR (CDCl3, 500 MHz) δ: 0.95
(3H, d J = 6.5 Hz Leu CH3); 1.0 (3H, d J = 6.4 Hz Leu CH3); 1.55 (1H, m J = 4.9 Hz/ 9.3 Hz/
-14.2 Hz Leu 3-Ha); 1.84 (1H, m, Leu 4-H CH); 1.91 (1H, m, Pro 4-Ha); 2.05 (1H, m, Pro 4Hb); 2.07 (1H, m, Leu 3-Hb); 2.12 (1H, m, Pro 3-Ha); 2.35 (1H, m, Pro 3-Hb); 3.54-3.61
(2H, m, Pro 5-Ha,b); 4.01 (1H, dd J = 9.2 Hz/ 4.4 Hz Leu -H); 4.13 (1H, dt J= 8 Hz/ =1 Hz,
Pro -H); 6.29 (1H, bs, NH). 13C NMR (CDCl3, 100 MHz) δ: 21.2, 22.7, 23.2, 24.6, 28.1, 38.6,
45.5, 53.4, 59.0, 164.9, 170.2. Based on the spectral data the molecular formula was
determined to be C11H18N2O2 by FABMS (m/z 211.12 [M+H]), calcd. for C11H18N2O2,
210.27.
Compound2:Cyclo(L-Pro-D-Met) (3S,8aR)-3 [2(methylsulfanyl)ethyl]hexahydropyrrolo
[1,2- a] pyrazine-1,4-dione: was obtained as white amorphous powder; Melting point:
148.65ºC; [α]30D -85.3° (c 0.10, EtOH); UV max : 205 nm (MeOH); 1H NMR (CDCl3)  2.06
(m, 2H, C6), 2.07 (m, 2H, C8), 2.13 (s, 3H, C10), 2.36 (m, 2H, C5), 2.71 (td, 2H, J = 2.5,
7.5, C9), 3.57 (m, 2H, C7), 4.11 (t, 1H, J = 7.5, C3), 4.21 (t, 1H, J = 5.5, C1), 7.67 (s, NH);
C NMR (CDCl3)  15.2 (C10), 22.6 (C6), 28.2 (C8), 28.9 (C5), 29.9 (C9), 45.4 (C7), 54.3
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(C1), 59.0 (C3), 165.6 (C2), 170.8 (C4). Based on the spectral data the molecular formula
was determined to be C10H17O2N2S by FABMS (m/z 229.10 [M+H]) calcd for m/z 229.13.
Compound 3: Cyclo (L-Pro-D-Phe): 3S,8aR)-3-benzylhexahydropyrrolo[1,2-a]pyrazine1,4-dione: was obtained as white amorphous powder; Melting point: 165.51ºC; [α]30D -76.91°
(c 0.04, EtOH); UV max : 208 nm (MeOH); 1H NMR (CDCl3)  1.88 (m, 2H, C6), 1.91 (m,
1H, C5), 2.32 (m, 1H, C5), 2.83 (dd, 1H, J = 10.0, 14.5, C8); 3.54 (m, 1H, C8), 3.59 (m, 2H,
C7), 4.05 (t, 1H, J = 7.5, C3), 4.28 (dd, 1H, J = 3, 9.9, C1), 5.98 (s, NH), 7.22-7.35 (m, 5H,
Ph);13C NMR (CDCl3)  22.5 (C6), 28.3 (C5), 36.8 (C8), 45.4 (C7), 56.2 (C1), 59.1 (C3),
127.5 (Phe), 129.1 (Phe), 136.0 (Phe), 165.1 (C2), 169.5 (C4). Based on the spectral data the
molecular formula was determined to be C10H17O2N2S by FABMS (m/z 245.12 [M+H]) calcd
for m/z 245.19.
Compound 4: Cyclo (L-Pro-L-Val): (3S,8aS)-3-(propan-2-yl)hexahydropyrrolo[1,2a]pyrazine-1,4-dione: was obtained as white amorphous powder; Melting point155.57 ºC;
[α]30D -229.0° (c 0.11, EtOH); UV max: 210 nm (MeOH);1H NMR (CDCl3) d0.92 (3H, d
J¼7.6Hz, CH3), 1.07 (3H, d J¼7.3, CH3), 1.87 – 1.95 (1H, m, H-4a), 2.00 – 2.11 (1H, m, H4b), 2.35 – 2.41 (2H, m, H-5), 2.59 – 2.67 (1H, m, H-10), 3.51 – 3.68 (2H, m, H-3), 3.94 (1H,
s, H-9), 4.08 (1H, t J¼7.6Hz, H-6), 5.99 (1H, brs, N-H). 13C NMR (100 MHz, CDCl3)
d169.71 (s, C-1), 45.07 (t, C-3), 22.33 (t, C-4), 28.48 (t, C-5), 60.27 (d, C-6), 164.60 (s, C-7),
58.72 (d, C-9), 28.32 (d, C-10), 19.22 (q, C-11), 16.03 (q, C-110). Based on the spectral data
the molecular formula was determined to be C14H16N2O2 by FABMS (m/z 197.12 [M+H])
calcd for m/z 196.20.
Compound 5 : 3,5-dihydroxy-4-ethyl-trans-stilbene: was obtained as solid powder;
Melting point: 220ºC; [a]D -193.31 (c, 0.01, MeOH); UV max : 280 nm (MeOH); IR (DR
1
mode) cm-1: 3700, 3500, 1620, 1590; H NMR (MeOD, 500MHz) : 87.46, 2H, d,J = 7 Hz;
7.25, 3H, m; 7.00, 1H, d, J = 16 Hz; 6.90, 1H, d, J = 16 Hz; 6.70, 2H, s; 4.90, 2H, bs (D20,
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exc.); 2.60, 2H, q, J = 7 Hz; 1.35, 3H, t, J = 7 Hz; H NMR (125 MHz, MeOD) 20.7, 29.74,
100.00; 106.86, 126.49, 127.66, 127.76, 154.98. Based on the spectral data the molecular
formula was determined to be CI6H17O2 by LC-MS (electrospray) (m/z 241 [M+H]), calcd.
for CI6H16O2, 240.
Compound 6 (3,5-dihydroxy-4-isopropylstilbene) was obtained as solid powder; Melting
point: 267ºC; [a]D -320.88 (c, 0.01, MeOH); UV max: 240 nm (MeOH); IR (DR mode) cm-1:
3417, 3028, 2960, 1618, 1578, 1424, 1359, 1267, 1159, 1130, 1071, 997, 961, 820 and 752
1
cm-1; H NMR (CDCl3; 300 MHz) d: 1.37, d (J 7.2 Hz) 6H, (CH3)2C; 3.45, m, 1H, CHMe2; 4.84, broads, 1H, OH; 6.50, s, 2H, ArH; 6.95, dd J 11.1 Hz, 2H, =CH; 7.33-7.35, m,
3H, ArH; 7.46-7.49, m,2H, ArH;
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C NMR (CDCl3; 125 MHz) d: 20.7, 29.74, 100.00;
106.86, 126.49, 127.66, 127.76, 154.98. Based on the spectral data the molecular formula
was determined to be CI7H18O2 by LC-MS (electrospray) (m/z: 255.0 [M+H]), calcd. for
CI7H18O2, 254.