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Articles tagged with: organocatalysis

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[7 Aug 2010 | 15 Comments | 20,156 views]
Cortistatins A (J, K and L) Pt. IV

Myers, Flyer, Si. Nat. Chem., 2010, AOP. DOI: 10.1038/nchem.794
Cortistatin is one of those targets like platensimycin that has attracted an almost unhealthy synthetic lust in the last few years, with three previous appearances in these interwebs (Baran, Nicolaou, Shair).  The reasons for both are the same – both have remarkable biological profiles, and both are of challenging complexity.  However, both are now what I’d call mature targets – in that the best disconnections have been tried, and that there are unavoidable methods that feature in most routes.  However, that …

Still In The RBF »

[18 Apr 2010 | 24 Comments | 17,080 views]

Bradshaw, Bonjoch, Etxebarria-Jard?´. JACS, 2010, ASAP. DOI: 10.1021/ja101994q.
It’s been a while since I wrote about a synthesis from Spain, so it’s nice to return with a rather sweet synthesis from the labs of Josep Bonjoch and his compatriot, Ben Bradshaw. Their efforts have been focused towards a sub-set of diterpenoids produced by Aspergillus, in which the decalin ring junction contains a pair of quaternary carbons.  That’s a pretty significant challenge by itself, but the rest of the decalin in subsituted in an all cis- arrangement, making for …

Still In The RBF »

[6 Sep 2009 | 31 Comments | 18,090 views]

MacMillan, Jones, Simmons. JACS, 2009, ASAP. DOI: 10.1021/ja9052366.
Now this is a popular target; I’ve covered syntheses by both Qin and Overman (with a related synthesis of vincorine by Qin too), both of which contain some really nice chemistry, and aren’t exactly lengthy.  However, this approach by MacMillan is incredibly concise, containing only nine steps, and starting with a commercially available indole.  To get to the key cyclisation precursor, a process of carbonylating the C-2 position by lithiation and addition of DMF, followed by a Horner-Wadsworth-Emmons olefination …

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[14 Jul 2009 | 20 Comments | 11,960 views]
Polyanthellin A

Johnson, Campbell, Qi. JACS, 2009, ASAP. DOI: 10.1021/ja904136q.
Sorry for the lack of blogging, folks – I’ve been feeling a bit under the weather, but I assure you, it’s not H1N1…  However, it seems like the res of the world is getting on with it, with several nice syntheses in JACS just now.  Lyconadin A is headed for Chemistry World, later this month, whilst plicatic acid is line behind polyanthellin A. Hopefully, sticking the latter into the Tot. Syn. search box (operated by trained hamsters) will …

Methods, Still In The RBF »

[8 Jun 2009 | 27 Comments | 13,976 views]
Physostigmine & Convolutamydine E

Barbas, Bui, Syed. JACS, 2009, ASAP. DOI: 10.1021/ja903520c.
Now, this is a bit of a fib already. I’m not entirely sure of Barbas’ reason for calling this paper a ‘formal total-synthesis of physostigimine’, as, whilst it is a formal synthesis, he actually stops at another natural product, esermethole.  Now, this is fine – and it’s still a formal synthesis of physostigimine, but it is moreso a total synthesis of esermethole.  Why he felt the need to call this a formal synthesis I don’t know.
It’s a shame …

Still In The RBF »

[2 Jun 2009 | 24 Comments | 11,441 views]
Ricciocarpin A

List, Michrowska. Nature Chem., 2009, AOP. DOI: 10.1038/nchem.215.
Another rather short blog post, but why wax-lyrical when the synthesis is short and sweet?  Ben List is still hammering-away at his niche in organocatalysis, this time reporting a rather nice domino reaction.  The target of the synthesis is a isolate of a liverwort, and possesses “potent molluscicidal activity” – not a biological effect I’d come across before.  It turns out that this natural product spells doom for Biomphalaria glabrata water snails…  and we’re still at a loss.  Water …

Still In The RBF »

[29 May 2009 | 13 Comments | 8,440 views]

van Maarseveen, Hiemstra, Wanner, Boots, Eradus and de Gelder. Org. Lett., 2009, ASAP. DOI: 10.1021/ol900888e.
Okay, jsut a little Org. Lett. to get my hand back into this blogging thing after being on holiday for a week.  The writing conditions have changed a little in Tot Syn towers, too – I’m now typing this on a new keyboard – a lovely aluminium Apple thing.  So I bid my old Microsoft ‘Natural’ keyboard goodbye, after six years of faithful service, and also six years of crud (putting …

Still In The RBF »

[17 May 2009 | 53 Comments | 20,776 views]
Eudesmane Terpenes

Baran, Chen. Nature, 2009, AOP. DOI: 10.1038/nature08043.
They say that the best defence is a good offence, so I’m going to start latterly – and remind (somewhat forcefully, if necessary) all prospective commenters that the folks at Nature decreed that this paper is worthy.  That’s good enough for me, so let’s avoid the tired arguments about suitability… </pre-emptive rant>
Anyway, what we’ve got here is typical of Baran – re-examination of chemical methodology of the past, and modernisation to solve problems in an orthogonal fashion.  Breaking that down, …

Featured, Still In The RBF »

[4 Jan 2009 | 27 Comments | 17,187 views]
Oseltamivir (Tamiflu) Pt. 6

Hayashi, Ishikawa and Suzuki. ACIEE, 2009, EarlyView. DOI: 10.1002/anie.200804883.
It’s back! Not just Tot. Syn., reanimated refreshed after a decent winter break, but Tamiflu too (thanks to all those who flagged this one up for me. In this case, in a (marginally) different guise, as what we’ve got here is Oseltamivir-free base, not the phosphate salt normally isolated. Not an important fact, but the salt formation probably makes quite a difference in-vivo…
However, that doesn’t matter a damn when the synthesis is a sweet at this. …

Still In The RBF »

[6 Apr 2008 | 26 Comments | 12,514 views]

MacMillan, Carpenter, Northrup, Chung, Wiener and Kim, ACIEE, 2008, EarlyView. DOI: 10.1002/anie.200800086.
Macrolide time again, and as this is David MacMillan, proline time too. The callipeltoside family of natural products has been reasonably popular, with syntheses from the usual suspects: Trost, Evans, Paterson, and Panek. However, all of those syntheses were of callipeltoside A, so this synthesis marks the first of callipeltoside C, including a reassignment of stereochemistry (the sugar fragment needed all is stereocenters inverted). Retro:

So far reasonably predictable/sensible disconnection – and you’ll note no …