Sarains: A New Class of Alkaloids from the Marine Sponge Reniera Sarai

Abstract

k n & e g a -s a g a i , a m a r i n e s p o n g e of t h e C e r a c t i n o m o r p h a s u b c l a s s e a s i l y c o l l e ct a b l e i n t h e Bay o f N a p l e s , i s c h a r a c t e r i z e d by a s e r i e s o f c y c l i c n i t r o g e nous compounds, which f o r many y e a r s h a v e r e s i s t e d a l l a t t e m p t s o f s t r u c t u r a l i n v e s t i g a t i o n . Complex s e p a r a t i o n s t e p s h a v e now l e d t o t h r e e new compounds, named s a r a i n -1 , s a r a i n -2 a n d s a r a i n -3 . T h e i r s t r u c t u r e s h a v e b e e n p a r t i a l l y d e t e rmined m a i n l y by a 5 0 0 MHz NMR s t u d y , u t i l i z i n g t h e l H -l H h o m o n u c l e a r and 'H-13C h e t e r o n u c l e a r NMR c h e m i c a l s h i f t c o r r e l a t i o n t e c h n i q u e s .

Marine-Derived Macrocyclic Alkaloids (MDMAs): Chemical and Biological Diversity

“…An investigation of the marine sponge Reniera sarai led to the identification of saraines 1-3 (45-47) [39], which belong to the 3-alkylpiperidine subclass ( Figure 6). The complexity of their structures delayed a complete elucidation until the mid-1980s.…”

“…They possess a pentacyclic skeleton that includes a trisubstituted alkene and a carbonyl group. The two cycles are supplied by linking the two heterocyclic systems with linear alkyl chains [39]. The three stereoisomers of saraines 1-3 have been reported and identified as isosaraines 1-3 (48-50) [40][41][42], which were also isolated from R. sarai as minor components.…”

Does the Chemical Diversity of the Order Haplosclerida (Phylum Porifera: Class Demospongia) Fit with Current Taxonomic Classification?

“…(l " Fig. 5) [73,74]. Both piperidine cycles are also connected through the C-4/C-5′ bond, but in the case of saraines A-C, other connections were established between both cycles.…”

Total Synthesis of (±)‐Haliclonacyclamine C

“…Hydrolysis, followed by nucleophilic attack by the nitrogen and dihydroxylation yields sarain A (1.5). Sarain -1 30 is another pentacyclic alkaloid which presumably arises from a 3, 4-linked bis-piperidine precursor. Starting from the iminium salt of the 3, 4-linked bispiperidine (1.63), oxidation at the γ-position of the macrocycle leads to ketone (1.64).…”