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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