Synthesis of Spirotryprostatin-B

SSG Group 2.6 (Gina DePolo, Jessica Ordonez, Chris Worsham)

Mechanism

1

The carbonyl of the Boc-group is protonated by TFA

2

Electron rearrangement occurs which stabilizes formal charges and consequently removes the tert-butyl group bonded to the ester of the Boc-group and forming a carboxyl group bonded to the nitrogen atom

3

The tert-butyl carbocation is deprotonated by the conjugate base of TFA and undergoes electron rearrangement to form 2-methyl-propene.� The nitrogen atom is protonated by the hydrogen atom of the carboxyl group and carbon dioxide is removed.� The nitrogen atom is protonated again by TFA to create a positive charge

4

The nitrogen atom is deprotonated by triethylamine

5

An intramolecular attack occurs between the lone pair on the nitrogen atom and a methyl ester on a different part of the molecule to form a di-charged six-membered ring

6

A lone pair on the oxygen anion rearranges to form a carbonyl and consequently remove the methoxy group.� The positively charged nitrogen atom is deprotonated by the methyoxy group to yield spirotryprostatin B (1)

7

Nitrogen is deprotonated by the alkoxide ion

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