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Dimethyl Gloiosiphone A   

14 May 2007 4,092 views 14 Comments

gloiosiphone.jpg
Takahashi, Doi, Iijima and Takasaki. JOC, 2007, ASAP. DOI: 10.1021/jo062546v.

At first, I loved the look of this synthesis; take one really simple acyclic precursor, dump in a little of everyone’s (or at least my) favourite palladium catalyst, and hey-presto – instant 5,5-spiro fused ring system. However, after that reaction, things go off-the-rails a little…

The substrate, as I said, was made very quickly, doing a double Tsuji-Trost allylic alkylation with the bis(phenylsulfonyl)methane on two allyl halides (okay, one is an allyl acetate…). They were then set to cyclise, using the same catalyst and ligand as in the past two reactions – however, they had to be careful not to get diallylation with only one electrophile.

gloiosiphone_1.jpg

No arguments – that is sweet. The only slight flaw was a lack of diastereomeric control at the OMPM centre, but that was soon to be oxidised, so was irrelevent. However, the process of getting to the target material was prolonged – fifteen further steps in total, and twelve to a known intermediate. Not exactly concise, but still a nice example of a domino intramolecular alkene insertion to a pi-allylpalladium intermediate, followed by Heck cyclisation.

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14 Comments

  • neo says:

    Cool synthesis. Will read the paper soon ! You have an extra carbon in the TS intermediate #1 it seems.

  • ZAL says:

    Nice synthesis, I always like domino Pd-catalyzed processes!. Not to bother you too much, but the sulphonyl groups are missing in intermediate 2 (not a TS, is it?), but they forgot them in the original paper too!

  • cheyanimal says:

    also palladium acetate has two acetates. (not to be a total pain)

  • Monkey says:

    A nice reaction, but a poor choice of target for its application, considering the number of steps afterwards.

  • TMTCl says:

    I love a good palladium cascade. Does anyone else find their little HMBC diagram weird? I can understand having an nOE correlation diagram, but I wouldn’t have wasted space on an HMBC…although they did get to use a lot of pretty colours.

  • pi* says:

    I agree with monkey, showcasing your methodology with a target shows that your method is useful. But you have to wonder if this synthesis is so long because of the key step.

  • ArrowPushingMonster says:

    I agree with monkey too…. (mostly cos I’ve never agreed with a monkey before…)

  • .... says:

    I once heard Andy Myers describe this research conundrum (i.e. total synthesis as a methodology showcase…only to find that the overall synthesis is inefficient) as “trying to bang square nails into round holes”

  • Tot. Syn. says:

    Apologies for the shocking quality control with this post – I’ll fix it later this evening. Lot’s more good stuff to blog this week too – Angewantde is full of lovely tot syn goodness.

  • willyoubemine says:

    Myers is right, its silly.

    What about posting on Myers Kedarcidin work…what an accomplishment. A good read and interesting chemistry.

  • accurate says:

    What kind of boss is A.G. Myers ? A nice one ?

  • milkshake says:

    I have heard good things about Andy Myers. Unlike many luminaries who act like conceited pricks, he is remarkably normal decent guy.

  • willyoubemine says:

    i have heard the same…tough but fair.