Biogenesis and Synthesis of Pinnaic Acids and Halichlorine

The structure of pinnaic acid (24) from the bivalve P muricata has been shown to be closely similar to that of halichlorine (26) from the marine sponge H. okadai. Each carbon atom has been tentatively numbered according to the supposed biogenetic formation of the N-C23 bond. Thus, these two bioactive metabolites may each be biosynthesized by symbiotic marine microorganisms.

Both pinnaic acids and halichlorine have attracted the attention of synthetic chemists. To date, 15 research groups have published synthetic studies [50]. The Danishefsky group has achieved the total synthesis of pinnaic acid [51,52] and halichlorine [53,54] in an asymmetric manner. Since pin-naic acid is a zwitterionic molecule, the NMR spectrum is quite sensitive to the measurement conditions. Recently, a racemic total synthesis of pinnaic acid (24) has been achieved (Scheme 5) [55]. A detailed comparison of the 1H-NMR spectra of both synthetic and natural samples supported Danishef-sky's revision of the configuration at C14.

racemic racemic

0 0

Post a comment