分子量3422の海洋猛毒・マイトトキシンの構造

抄録

Maitotoxin was first discovered as one of the causative toxins responsible for ciguatera, which is a form of seafood poisoning prevalent in coral reef area. The structure (1) has been elucidated to be a polyketide compound with a molecular weight of 3422 Da, which makes the toxin the largest natural non-biopolymer known to date. The structure is partly reminiscent of brevetoxins or ciguatoxins, which comprise trans-fused polycyclic ethers, though maitotoxin possesses about three times as many ether rings as does brevetoxin B. In this paper we review the structure elucidation of maitotoxin with the main focus on spectroscopic methodology, particularly on tandem mass spectrometry (MS/ MS), three-dimensional NMR spectra, and stereostructural analysis using NOE and ³J/_H.H data coupled with force field calculations.
Collisionally Activated Dissociation (CAD) MS/MS spectra with a negative FAB ionization were successfully measured for fragment B (MW. 2328 Da) of maitotoxin and revealed fragment ions from which the sizes and sequences of ether rings easily were derived. Three dimensional NOESY-HMQC with pulse field gradient was determined for a ¹³C-enriched specimen (at about 4%) and provided 64 ¹³C-edited NOESY spectra, some of which brought essential NOE information regarding the mode of ether cyclization and stereochemistry.