Synthetic Studies on Hemicalide: Development of a Convergent Approach toward the C1–C25 Fragment

A synthesis-enabled relative configurational assignment of the C31-C46 region of hemicalide

With 21 unknown stereocentres embedded in spatially separated stereoclusters, the cytotoxic polyketide hemicalide represents a seemingly intractible structural assignment problem. Herein, through the targeted synthesis of configurationally defined fragments, as...

A synthesis-enabled relative stereochemical assignment of the C1-C28 region of hemicalide

Through synthesising both candidate diastereomers of a model C1-C28 fragment of the potent cytotoxic marine polyketide hemicalide, an assignment of the relative configuration between the C1-C15 and C16-C26 regions has been achieved. By detailed NMR comparisons with the natural product, the relative stereochemistry between these two 1,6-related stereoclusters is elucidated as 13,18-syn rather than the previously proposed 13,18-anti relationship. A flexible and modular strategy using an advanced C1-C28 ketone fragment 22 is outlined to elucidate the remaining stereochemical features and achieve a total synthesis.

Toward the stereochemical assignment and synthesis of hemicalide: DP4f GIAO-NMR analysis and synthesis of a reassigned C16–C28 subunit

Computational DP4f GIAO-NMR analysis resulted in a stereochemical reassignment of hemicalide, supported by improved NMR correlations with a C13–C25 fragment.