Denticulatin A and

De Brabander, J., Oppolzer, W. Enantioselective total synthesis of (-)-denticulatins A and B using a novel group-selective aldolization of a meso dialdehyde as a key step. Tetrahedron 1997, 53, 9169-9202. 

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. 

Hoffmann and co-workers completed the first synthesis of both denticulatins via a C9-C10 aldol bond construction (Scheme 9-70) [87], In this case, aldehyde 266 was assembled using asymmetric crotylboration reactions to introduce the C4-CS stereocenters. The (Z)-boron enolate 267 was then reacted with aldehyde 266 to afford the desired anh-Felkin adduct with 80% selectivity where the minor diastereomer resulted from reaction of the enantiomer of the starting ketone. Unfortunately, the C5-PMB ether protecting group could not be removed without epi-merization at C o, and denticulatins A and B were formed in equimolar amounts. 

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. 

Paterson, I. and Perkins, M.V. (1992) Studies in polypropionate synthesis stereoselective synthesis of (—)-denticulatins A and B. Tetrahedron Lett., 33,801-804. 

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