Spironaamidine, a new spiroquinone-containing alkaloid from the marine sponge Leucetta microraphis

Chagosendines A – C, New Metal Complexes of Imidazole Alkaloids from the Calcareous Sponge Leucetta chagosensis

“…Biogenetically, these complexes is postulated to be charged by numerous metalloenzymes that require Zn 2+ for catalytic activity. Some of them were tested to exert antimicrobial activity against pathogen bacterial strains S. aureus , while the ligand alkaloids exhibited cytotoxic toward tumor cell lines, antimicrobial, leukotriene B4 receptor antagonistic, and epidermal growth factor (EGF)‐stimulated DNA synthesis inhibitory activities . In our ongoing study on the chemical diversity and the biological activity from the marine benthic organisms, a bright yellow sponge of Leucetta chagosensis was collected from the South China Sea.…”

Studies towards the Leucetta‐Derived Alkaloids Spirocalcaridine A and B – Possible Biosynthetic Implications

“…[7] The final and most recently isolated group of alkaloids belonging to this family of sponges is the most highly oxygenated comprising calcaridine A ( 8 ), [8] spirocalcaridines A ( 9 ) and B ( 10 ), [8b] spiroleucettadine ( 11 ) [9] and spironaamidine ( 12 ). [10] …”

Total Synthesis of (−)‐Spiroleucettadine

“…[2] Thediscovery of spiroleucettadine was met with international interest, not only as ar esult of its antibacterial activity (minimum inhibitory activity,M IC < 6.25 mgmL À1 against Enterococcus durans)b ut also because of its seemingly unprecedented trans-fused 2-iminoimidazole-oxolanec ore. Thel egitimacyo ft his structure (Figure 1, 1)b ecame uncertain following several failed attempts by independent research groups [3] to carry out the requisite hypervalentiodine-mediated oxidative spirocyclization, and the viability of the 5,5-trans-fused system and its ability to form the seemingly unstable ortho-amide-type functionality were called into question. [4] Ther evised structure of spiroleucettadine is one of the more oxidized congeners of the Leucetta alkaloids,similar to spirocalcaridine A,B (5;F igure 1) [5] and the more recently discovered spironaamidine (6). [4] Ther evised structure of spiroleucettadine is one of the more oxidized congeners of the Leucetta alkaloids,similar to spirocalcaridine A,B (5;F igure 1) [5] and the more recently discovered spironaamidine (6).…”

“…Theanalytical data for spiroleucettadine was revisited, and the structure was revised to 2,w hich was further supported by DFT calculations and X-ray crystallography. [6] Attempts to access the Leucetta family of structures have typically relied on the elaboration of an existing imidazole framework rather than the de novo construction of the heterocycle. [6] Attempts to access the Leucetta family of structures have typically relied on the elaboration of an existing imidazole framework rather than the de novo construction of the heterocycle.…”

“…Originally assigned structure (1)and revised structure (2)o f spiroleucettadine, representative Leucetta alkaloids naamidineA(3), naamine A( 4), spirocalcaridine A( 5a,R= H), spirocalcaridine B( 5b, R = Me), spironaamidine(6), and failed oxidative spirocyclization towards 1.Boc = tert-butoxycarbonyl, PIFA = phenyliodine bis(trifluorocetate).…”