From Pseudopterogorgia

Heckrodt TJ, Mulzer J (2005) Marine Natural Products from Pseudopterogorgia Elisabe-thae Structures, Biosynthesis, Pharmacology and Total Synthesis. 244 1-41 Heinmaa I, see Samoson A (2005) 246 15-31 Helm L,see Toth E (2002) 221 61-101 Helmboldt H, see Hiersemann M (2005) 243 73-136 Hemscheidt T (2000) Tropane and Related Alkaloids. 209 175-206... 

Marine Natural Products from Pseudopterogorgia elisabethae 3... 

The following gives an overview of the natural products isolated to date from Pseudopterogorgia elisabethae. The structures of these compounds were proposed on the basis of comprehensive spectral analyses, chemical transformations, and X-ray crystallographic analyses. 

Compounds from Pseudopterogorgia elisabethae can be classified according to their carbon skeletons. So far 15 carbon skeletons have been identified which are based on the serrulatane skeleton. Various cyclizations (see also Sect. 3.1, Scheme 1) of this precursor lead to newpolycycHc structures (e.g., amphilectanes, ehsabethanes, etc.) that are starting points for new degradation products (seco-, nor-, bisnor-, etc. compoimds). 

A C9-C14 cycHzation forms the ring C and leads to the amphilectane skeleton which is foimd for instance in pseudopterosins A-F (10, aglycone) [10] isolated from Pseudopterogorgia elisabethae extracts stemming from a Bahamian collection site (Fig. 5). This class of natural products can be characterized as... 

Another tetracyclic carbon skeleton, named cumbiane, has been isolated from Pseudopterogorgia elisahethae. Its representatives are the diterpenoids cumbiasin A (33) and B (34) [20] their structures and relative configurations were elucidated by interpretation of a combination of spectral data. The six-membered ring D was formed by connecting CIO and C16 of an elisabethane carbon skeleton. The carbocyclic skeleton of the cumbiasins is unprecedented and represents a new class of C20 rearranged diterpenes. The tricyclic seco-cumbiane skeleton is derived from the cumbiasins by cleavage of the C15-C16 bond. Due to intramolecular cyclizations two additional oxo-heterocycles are present in cumbiasin C (35) [20] (Fig. 7). 

A further tetracyclic metabolite from Pseudopterogorgia elisabethae possessing the unprecedented cage-like colombiane carbon skeleton is represented by colombiasin A (36) [21]. The ring D of the colombiane skeleton arises from a C12-C2 cyclization of an elisabethane-based precursor. Experimental data were not obtained to define the absolute stereochemistry of 36 this task was later accomplished by total synthesis (see Sect. 4.6). 

As shown in the previous section, the structural diversity found among the plethora of natural products isolated from Pseudopterogorgia elisabethae is indeed remarkable. Scheme 1 gives an overview of the biosynthetic pathways to the different carbon frameworks produced by Pseudopterogorgia elisabethae. 

An alternative pathway (Scheme 8) could start from the two regioisomers 5 and 6, both isolated from Pseudopterogorgia elisabethae. Thus, after phosphorylation or protonation followed by elimination to dienylquinone 46, intramolecular cyclization would generate zwitterionic intermediate 47. Hydride... 

Marine Natural Products from Pseudopterogorgia Elisabethae Structures, Biosynthesis, Pharmacology and Total Synthesis... 

Miller, S.L. Tinto, W.F. Yang, J.-P. McLean, S. Reynolds, W.F. (1995) 9,1 l-seco-24-Hydroxydinosterol from Pseudopterogorgia americana. Tetrahedron Lett., 36, 1227-8. 

Fig. 8 Natural products derived from Pseudopterogorgia elisabethae...

Scheme 1 Terpenoid carbon skeletons from Pseudopterogorgia elisabethae.

---