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Articles tagged with: aldol

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[7 Dec 2011 | 23 Comments | 21,715 views]
Taxane Skeleton

Baran, Mendoza, Ishihara. Nature Chem., 2011, EarlyView. DOI: 10.1038/nchem.1196   
Hmm… I’m still not convinced about whether I should really post on this paper, but I’m interested in it, so to hell with the rules!  What we’ve got here is a sort-of meta-synthesis; Baran doesn’t actually make any of the taxane natural products, but demonstrates an extremely neat synthesis of a potential common precursor.  The theory behind the work is related to previous Baran diatribes, where he points out that too many steps in syntheses simply oxidise and reduce the same …

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[6 Aug 2011 | 17 Comments | 15,674 views]
Omphadiol

Romo, Liu. ACIEE, 2011, 50, 7537-7540. DOI: 10.1002/anie.201102289
Guest Blogger: SPF
What if I’d ask you to synthesize this little molecule with six neighbouring stereocenters from biologically available material? Oh, by the way you can’t use any protecting groups and keep it short! Sounds impossible? Not according to Romo et al.. They’ve achieved the synthesis of this stereo-dense molecule in 10 steps from (R)-carvone (Mmmhhh spearmint). (+)-Omphadiol belongs to the africanane (guess where they grow) family of sesquiterpenes. Its brothers and sisters show some significant bioactivity, but due to insufficient …

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[16 Jun 2011 | 29 Comments | 20,264 views]
Cyanolide A Aglycon

Rychnovsky, Gesinski. JACS, 2011, ASAP. DOI: 10.1021/ja204228q
Guest Blogger: See-Arr-Oh
When I first saw the dimeric gamma-substituted pyran motif in this molecule, I said “Gotta be Rychnovsky” (or maybe Wender).   Throughout his career at UC-Irvine, Scott Rychnovsky has been the master of the TMS-promoted diastereoselective Prins cyclization, which he has applied to the synthesis of at least 10 macrolides.  Until now, however, none have been attempted sans protecting groups!
Cyanolide A was isolated in 2010, and it’s already been the target of four total syntheses.  Perhaps this is due to …

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[24 Oct 2010 | 116 Comments | 61,552 views]
Lycoflexine

Ramharter, Mulzer, Weinstabl. JACS, 2010, 132, 14338-14339. DOI: 10.1021/ja107533m
I love the fact that one can just look at a molecule and then guess the author of the synthesis.  And when I first glanced at Lycoflexine, the name Johann Mulzer was at the top of my mind.  (However, on closer inspection, the starred author is one Juergen Ramharter, even though Mulzer is also named…)  This makes me smile for two reasons – firstly, Mulzer always works on small, yet interesting targets.  Secondly, I routinely learn something new in his work.
To say …

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[24 Jun 2010 | 29 Comments | 17,307 views]
Fastigiatine

Shair, Liau, JACS, 2010, ASAP DOI: 10.1021/ja104575h.
After wading through the Heathcock paper last week, I’m glad that today’s topic of discussion is a little shorter and easier to read.  (Seriously, part of me hates reading paper older that the 90′s as the style used in the schemes and figures is so difficult to follow.  Some of those 1960′s JACS papers are a real slog to get through – but worth it, normally….)
The target of choice today is Fastigiatine, a member of the Lycopodium alkaloid family, a popular …

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[25 Feb 2010 | 30 Comments | 16,451 views]
Communesin F

Weinreb, Liu, Seo. ACIEE, 2010, EarlyView. DOI: 10.1002/anie.200906818.
Quite a congested little beast, eh?  I felt that a 3D representation might help show the almost cage-like structure.  Also, having been at a Med-Chem conference for the last few days, I’ve been seeing everything in 3D.  I haven’t seen many molecules with this skeleton before, so I was surprised to see that it was isolated in Penicillium mold; however, this was found growing on a marine algae, so I guess that makes for some pretty special biosynthetic machinery. …

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[18 Jan 2010 | 16 Comments | 16,286 views]
Hyperforin

Shibasaki, Kanai, Shimizu, Shi, Usuda. ACIEE, 2010, EarlyView. DOI: 10.1002/anie.200906678. ; Shibasaki, Kanai, Kuramochi, Usuda. Org. Lett., 2004, 6, 4387. DOI: 10.1021/ol048018s. 
Three amazingly tough targets completed in (almost) as many months – you can’t tell me that total synthesis is stifled.  Hyperforin has been staining the white-boards of many a lab for decades – the isolation (reported in Antibiotik…) was way back in ’71, and has resisted synthesis until now.  Shibasaki himself has been working on it for quite a while, as you’ll have seen in the header – a key …

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[22 Oct 2009 | 30 Comments | 19,452 views]
Codeine

Magnus, Sane, Fauber, Lynch. JACS, 2009, ASAP. DOI: 10.1021/ja9085534.
I don’t think we’ve covered many targets I’ve actually ingested; and I’ve done most of the family too.  The morphine was a bit ‘meh’, as I was so out-of-it I couldn’t really appreciate it.  But the dihydrocodine was the good-stuff – really took the edge off my pluracy.  However, the withdrawal symptoms were kinda harsh.  Other members of this historic family of natural products include galanthamine and narwedine, neither of which I’ve encountered before.  Philip Magnus has, though, as …

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[30 Aug 2009 | 42 Comments | 16,242 views]
6-deoxyerythronolide B

White, Stang. Nature Chem., 2009, AOP. DOI: 10.1038/nchem.351.
Nice to see a bit of total synthesis in Nature Chemistry this month – but to be fair, this is more about the organometallics than the macrolide.  But if you’re going to prove some methodology – especially, as in this case, macrolactonisation, this is a good target to work on.  6-deoxyerythronolide B (6-dEB) is a typical polyketide macrolide, and I mean that chemically, as the configuration of the stereocenters is very much the norm.  This meant two things – …

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[25 Aug 2009 | 8 Comments | 12,191 views]
Sorangicin A – pt. 2

Smith, Dong, Brenneman, Fox. JACS, 2009, ASAP. DOI: 10.1021/ja9052366.
Read the first post?  Good.  Let’s get on with the one remaining fragment, a further DHP.  Work on this fragment was conducted via a coupling of an enone with the ready-elaborated sidechain – reaction that might be a little sluggish, as the enol functionality is again working against the group.  However, forming a cuperate of the vinyl bromide solved this, allowing a highly selective and reasonably high yielding reaction (60%, 20:1 d.r.).  BTW, the two fragments weren’t particularly …