Total Synthesis Blog

Today, total synthesis of hyptolide which was published in Tetrahedron Letters. Structure of target molecule is drawn below (click on images to enlarge them ):

Authors wrote about some “important biological activities” and “interesting pharmacological properties” and they wrote nothing more So, what do we have here? Well, four stereocentres, two double bonds and α,β-unsaturated δ-lactone ring makes hyptolide really nice target molecule.

Hyptolide is present in plants from family called Lamiaceae, especially in genera Hyptis and Syncolostemon. There are several compounds related to hyptolide: spicigerolide, anamarine and synrotolide. Their are shown below.

I’ve tried to plan the synthesis of hyptolide and my proposition of retrosynthesis is presented at next images.

I hope that everything is clear (P means some protecting groups)

The real retrosynthesis of hyptolide:
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Today, some nice-looking target – isolated from germinating sunflowers (Helianthus annus L.) – (+)-Sundiversifolide:

Nice structure and nice name (however, I prefer snow ). (+)-Sundiversifolide exhibits some interesting biological properties. For example it can inhibit root growth of some plants. Also it can inhibit (in small concentrations – about 100 μM) germination of some fungi species and therefore it can be used as natural herbicide.

Below I’ve shown my retrosynthetic approach to (+)-Sundiversifolide:

(Click on image to enlarge it)

The key steps involve Diels-Alder cyclization, ring expansion (with use diazo compound) and TPAP-promoted cyclization (see also Total Synthesis of Bruguierol C for other application of that key reaction). I’m waiting for your opinions.

The real retrosynthesis of (+)-Sundiversifolide is shown below:
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