Eleutherobin aglycone

For a tandem Diels-Alder/fragmentation approach to the eleutherobin aglycone, Winkler et al. used Marshall s protocol in an early step of the synthesis. The building block 95 was prepared in that way (Scheme 15.24) [56]. 

In the laboratory of J.D. Winkler, the synthesis of the carbon framework of the eleutherobin aglycon was developed using a tandem Diels-Alder reaction and a Grob fragmentation as key steps.The tricyclic fragmentation precursor was subjected to potassium carbonate in DMF at 75 °C to afford the fragmentation product in 68% yield via a dianion intermediate that underwent a spontaneous hemiketalization. 

Cycloaddition reactions of dienes with allenes are used in the synthesis of natural products. For example, the [4+2] cycloaddition reaction of the furan-tethered diene 443 with the allene 444 affords the carbon framework of the eleutherobin aglycone 445 . 

Nicolaou s total synthesis of a marine antitumor agent, eleutherobin [22] (Scheme 12.24), involves the attachment of D-arabinose to the aglycon intermediate. Thus, the glycosidation of the (-F )-carvone-derived hydroxy aldehyde 210 and the trichloroacetimidate 211, derived from... 

Extraction from large quantities of this soft coral yielded, in the less-polar phase, the aglycone of eleutherobin accompanied by three other derivatives, caribaeorane, 15-hydroxycaribaeorane and methylcaribaeorane (Britton... 

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