Structure of sibirine

Total Synthesis via Biomimetic Late-stage Heterocyclization, Assignment of the Relative Configuration and Biological Evalu-ation of the Nitraria Alkaloid (±)-Nitrabirine

“…1 The simple Nitraria spiranic alkaloids include (+)-nitramine (1), (+)-isonitramine (2), ( ̶ )-sibirine (3), ( ̶ )-sibirinine (4), (±)-nitrabirine ( 5) and (±)-nitrabirine-N-oxide (6) (Figure 1), which have been isolated from two species of the Nitraria genus, namely Nitraria schoberi (for 1) 2 and Nitraria sibirica (for 2, 3, 4, 5, and 6). [1][2][3][4][5][6] Structurally, the simple Nitraria spiranic alkaloids comprise a 2-azaspiro [5.5]undecan-7-ol framework with a central chiral quaternary carbon centre. Additionally, aminal formation bridging the secondary amine in the 2-position with the hydroxy moiety in the 7-position leads to the tricyclic core of (-)sibirinine (4).…”

“…[1][2][3][4][5][6] Structurally, the simple Nitraria spiranic alkaloids comprise a 2-azaspiro [5.5]undecan-7-ol framework with a central chiral quaternary carbon centre. Additionally, aminal formation bridging the secondary amine in the 2-position with the hydroxy moiety in the 7-position leads to the tricyclic core of (-)sibirinine (4). The structures of nitrabirine (5) and nitrabirine-N-oxide (6) contain an additional annulated imidazole ring in their tricyclic tetrahydro-5'Hspiro[cyclohexane-1,8'-imidazo [1,2-a]pyridin]-2-ol skeleton (Figure 1).…”

Total Synthesis via Biomimetic Late-stage Heterocyclization, Assignment of the Relative Configuration and Biological Evalu-ation of the Nitraria Alkaloid (±)-Nitrabirine

“…1 The simple Nitraria spiranic alkaloids include (+)-nitramine (1), (+)-isonitramine (2), ( ̶ )-sibirine (3), ( ̶ )-sibirinine ( 4), (±)-nitrabirine ( 5) and (±)-nitrabirine-N-oxide (6) (Figure 1), which have been isolated from two species of the Nitraria genus, namely Nitraria schoberi (for 1) 2 and Nitraria sibirica (for 2, 3, 4, 5, and 6). [1][2][3][4][5][6] Structurally, the simple Nitraria spiranic alkaloids comprise a 2-azaspiro [5.5]undecan-7-ol framework with a central chiral quaternary carbon centre. Additionally, aminal formation bridging the secondary amine in the 2-position with the hydroxy moiety in the 7-position leads to the tricyclic core of (-)sibirinine (4).…”

Salts of spiro-derivatives of benzo[f]quinoline and several natural carboxylic acids

“…and contained structural features of the alkaloid nitramine (2) [2,3], which is found in the aerial part of Nitraria sibirica Pall. The goal of the present work was to develop a preparative synthesis of new biologically active salts of spiro-derivatives of benzo[f]quinoline 1a and b with several natural carboxylic acids 3 (ketopinic, 10-camphorsulfonic, 3-exoisocamphanonesulfonic, abietic, benzoic, L-alanine, L-valine, L-leucine, L-isoleucine, nicotinic, succinic, 4,4′-biphenyldicarboxylic, and 2-hydroxy-4,4′-biphenyldicarboxylic).…”