Carboline Alkaloids fromTrigonostemon lii

Abstract

Three types with six new carboline alkaloids, trigonostemonines A-F (1- 6), were isolated from the roots and stems of Trigonostemon lii. Their structures were elucidated by spectroscopic analyses. It is the first time that beta-carboline alkaloids have been reported in Trigonostemon species. Trigonostemonine F (6) exhibited moderate cytotoxic activity against HL-60 with an IC (50) value of 16 microM.

Structurally Diverse Alkaloids from the Seeds of Peganum harmala

“…The spectroscopic data of compound 6 were similar to trigonostemonine E. 21 Comparison of the 1 H and 13 C NMR data (Tables 2 and 3) with those of trigonostemonine E revealed that compound 6 had a similar 1-(quinolinyl)-3,4-dihydro- β -carboline skeleton. Unlike trigonostemonine E, the O -methyl group was located at C-9.…”

“…Pegaharmine G ( 6 ) was isolated as a yellow, amorphous powder, and its molecular formula was determined as C 21 H 17 N 3 O based on a positive HRESIMS ion at m / z 328.1440 [M + H] + (calcd for 328.1444). The spectroscopic data of compound 6 were similar to trigonostemonine E . Comparison of the 1 H and 13 C NMR data (Tables and ) with those of trigonostemonine E revealed that compound 6 had a similar 1-(quinolinyl)-3,4-dihydro-β-carboline skeleton.…”

“…Pegaharmine J ( 9 ) was isolated as a yellow, amorphous powder, and its molecular formula was assigned as C 13 H 12 N 2 O 2 based on a positive HRESIMS ion at m / z 229.0975 [M + H] + (calcd for 229.0972). Its UV spectrum had absorption maxima at 242 and 301 nm, indicating that a β-carboline chromophore was present. , Analysis of the NMR data of 9 (Tables and ) revealed the presence of a β-carboline skeleton, which was in accord with an aromatic ABX spin system (δ H 8.06, 1H, d, J = 8.6 Hz; 6.84, 1H, dd, J = 8.6, 2.1 Hz; 7.12, 1H, d, J = 2.1 Hz) and a pair of ortho -coupled protons (δ H 8.19, 1H, d, J = 5.0 Hz; 7.89, 1H, d, J = 5.0 Hz). In addition, the key HMBC cross-peaks of H-14 (δ H 4.92, 2H, d, J = 5.2 Hz) to C-13 (δ C 133.6) and C-1 (δ C 144.2) indicated that a hydroxymethyl group was located at C-1.…”

Total Synthesis, Stereochemical Assignment, and Biological Activity of All Known (−)-Trigonoliimines

“…Notably, the presence of regioisomeric pairs is commonly observed in the trigonostemon alkaloids family (Figure 1). 37 Hence, we reasoned that the formation of both regioisomers during the oxidation of bistryptamine precursor might explain the biodiversity observed in the trigonostemon alkaloids family. Notably, modification of bistryptamine 32 through an N1-protection with various electron withdrawing groups greatly altered their chemical properties toward oxidation.…”

Concise Total Synthesis and Stereochemical Revision of all (−)-Trigonoliimines

“…In fact, simple exposure of bistryptamine 16 to air over 12 days resulted in autoxidation to (±)-hydroxyindolenines 17 and 18 ( 17:18 = 1.5:1) in 27% yield along with recovered 16 (65%). Interestingly, the presence of regioisomeric pairs is commonly observed in the trigonostemon alkaloids family 15 (Figure 1) and the major autoxidation product (oxidation of 6-methoxy-indole substructure) is consistent with the major isolated trigonoliimines A ( 1 ) and C ( 3 ). 1 Given the rapid oxidation of bistryptamine 16 , and based on observations on stereoselective oxidation of related derivatives, 4,5,7,16 we focused our attention on the use of oxaziridines.…”