Oxathiazepino-eudistomins

The eudistomins from E. olivaceum extract readily into a non-polar phase, toluene (26-28) or dichloromethane (29), and require repeated chromatographic steps to separate one from another, especially within a related class. Separation in some cases is especially problematic (28, 29) for example, eudistomins N (3) and O (4) proved inseparable at the time they were reported. Structure elucidation relied heavily on interpretation of spectral data, especially 500 MHz NMR and mass spectra (26) several members of the series have now been synthesized (see Section 3). Eudistomin K has been crystallized and subjected to X-ray analysis (32) revealing the absolute configuration of the oxathiazepino-eudistomins. 

The PS reaction has been used by Still and coworkers to prepare woodinine (14), eudistomin T (17), and a eudistomidin B analog (Scheme 8) (125, 126). Woodinine was prepared from l-proline via intermediate 160 the diastereoselectivity of the PS reaction provides roughly an 85/15 ratio of the desired trans isomer. Intermediate 161 has previously been elaborated into eudistomins I (8) (28) and eudistomin H (7) can be derived directly from eudistomin I (127). That woodinine derives from an L-amino acid while the oxathiazepino-eudistomins derive from a D-amino acid is curious from a biosynthetic point of view. 

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