total synthesis of diterpenoid steenkrotin a - boston...

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Saiyong Pan, Jun Xuan, Beiling Gao, An Zhu, and Hanfeng Ding

Department of Chemistry, Zhejiang University, 148 Tianmushan Road,

Hangzhou 310028 (China)

Angew. Chem. Int. Ed. 2015, 54, 6905 –6908.

Total Synthesis of Diterpenoid Steenkrotin A

Introduction Steenkrotin A was first isolated by Hussein and co-workers in 2008 from the extract of leaves of C. steenkampianus.

It has a [3,5,5,6,7] pentacyclic skeleton and eight stereocenters (including one quaternary center).

1

Presented by Yuanzhe Zhang, Liu group.

2

Retrosynthetic route

3

Towards

compound 7

4

O-H bond

activation

5

Carbonyl-ene

reaction

E(SmI2+/SmI2) = 1.41 V (THF)

E(SmI2+/SmI2) = 1.79 V (THF + 4 eq. HMPA)

6

Ueno-Stork

Reaction

7

Ketyl-olefin

cyclization

DMP mechanism has been illustrated in the previous slide.

8

Aldol

condensation

9

Epimerization

10

Cascade method

11

Final step

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