Siphonaria Denticulatins

Denticulatins A and B. The denticulatins A (250) and B (251) were isolated in 1983 from the marine mollusc Siphonaria denticulata and are highly oxygenated structures with seven contiguous stereocenters (Scheme 9-67). Three total syntheses of these molecules rely upon aldol reactions to assemble triketone 252. a key intermediate, forming either the Ciq-Ch or C9-C10 bond at a late stage. 

Diemenensin-A (882) inhibited Staphylococcus aureus and Bacillus subtilis at 1 pg/disc and 5 pg/disc, respectively, and inhibited cell division in the fertilized sea urchin egg assay at 1 pg/mL. Another new polypropionate antibiotic with a y-hydroxy-a-pyrone ring, pec-tinatone (884) was isolated from Siphonaria pectinata (592). S. denticu-lata furnished two isomeric polypropionate metabolites, denticulatin A (885) and B (886) (593). Denticulatin A (885) was ichthyotoxic at 10 pg/mL while 886 was reported to be toxic at 30 pg/mL. Norpectina-tone (887) and the E- and Z-isomers 888 and 889 of a related furanone were constituents of the Chilean pulmonate S. lessoni (594), and a cyclic hemiacetal (890) as well as an associated ketol ester (891) were reported as metabolites of S. australis (595). Hochlowski et al. (596) investigated four other Siphonaria species and isolated siphonarin-A (892)... 

Denticulatins A and B 39 are one of several polyketide-based natural products that have been synthesized using a SAMP/RAMP hydrazone alkylation as a key step (Scheme 7.6A). The denticulatins are intriguing polypropionate metabolites isolated from Siphonaria denticulata, a class of air-breathing mollusks. Denticulatins A and B were first isolated from these mollusks in 1983 off the coast of... 

Ziegler EE, Becker MR. Total synthesis of (—)-denticulatins A and B marine polypropionates from Siphonaria denticu-lata.J. Org. Chem. 1990 55(9) 2800-2805. 

---