{"id":9,"date":"2026-05-10T03:48:57","date_gmt":"2026-05-10T03:48:57","guid":{"rendered":"https:\/\/wordpress.yangmao.cfd\/?p=9"},"modified":"2026-05-10T03:48:57","modified_gmt":"2026-05-10T03:48:57","slug":"acyl-anion-equivalent-strategy-the-total-synthesis-of-curvulamine","status":"publish","type":"post","link":"https:\/\/wordpress.yangmao.cfd\/?p=9","title":{"rendered":"Acyl Anion Equivalent Strategy: The Total Synthesis of Curvulamine"},"content":{"rendered":"\n

An acyl anion is unstable on its own, but can be very stable if we use TMSCN to temporarily mask it.<\/strong><\/h2>\n\n\n\n

The carbonyl group is a strong electrophile; it is often recognised as a partially positively charged group. But from a retrosynthetic plan, people found they already had an electrophile, so the acyl group had to act like an anion that needs to be partially negatively charged.<\/p>\n\n\n\n

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Now let’s have a look at a simple retrosynthesis of a compound. There are many potential reactions we can apply here to obtain this compound. The simplest one may be the aldol condensation, if we break it down between carbon 4 and 5.<\/p>\n\n\n\n

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If we decide to break down carbon 3 and 2, things begin to get a bit complex. If you want to use metal, a reaction such as the Corey-Posner Reaction might be applicable. But what if you don\u2019t want to use metal?<\/p>\n\n\n\n

We need a potential reaction 3 as shown below. One can assume that the right-hand side subunit is an alkyl halogen, as an electrophile, while the left-hand side is an acyl anion. The question is how we could obtain such a species in practice, given the acyl group\u2019s positive charge.<\/p>\n\n\n\n

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One way to do this is to take TMSCN as a masking group by addition to the acyl group, which can then be deprotonated, serving as a negatively charged nucleophile instead of the electrophile. After nucleophilic addition to an alkyl halide, it is unmasked back into an acyl group.<\/p>\n\n\n\n

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As the green box above shows, we treat the TMSCN-masked anion as an acyl anion equivalent in practice. The reason why this could work nicely is partly due to the strong electron-withdrawing nature of the CN group, which can stabilise the negative charge after LDA deprotonation.<\/p>\n\n\n\n

This strategy was applied in the total synthesis of (-)-Curvulamine by\u00a0the Maimone Group<\/a>\u00a0at UC, Berkeley. We only show part of their synthesis plan that involves our topic here.<\/p>\n\n\n\n

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What they need is an acyl group similar to the one we discussed above. They also adopted the same strategy, using TMSCN as a masking group, in a three-step one-pot reaction: <\/p>\n\n\n\n