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Articles Archive for July 2006

Still In The RBF »

[30 Jul 2006 | 12 Comments | 7,250 views]

Fürstner, Nevado, Tremblay, Chevrier, Teplý, Aïssa, and Waser. ACIEE, 2006, Early View. DOI: 10.1002/anie.200601860.
An interesting read by Fürstner, into the synthesis of this cytotoic and anticancer polyene macrolide. The most active member of the family, it’s certainly a useful target, but one would think that the disconnections for the retrosynthetic analysis would be relatively straight-forward. However, that tempting macrolactonisation failed so their approach to this campaign had to be revised. They decided, then, to complete the macrocyclisation using a RCM strategy. (Two other papers by the authors are referenced as …

Still In The RBF »

[27 Jul 2006 | 32 Comments | 10,533 views]

Porco, Su, Lei, Bardhan and Rychnovsky. ACIEE, 2006, Early View. DOI: 10.1002/anie.200602854.
So the dust has settled – and it looks like Rychnovsky was right. But lets disregard the controversy for now, and look at the synthesis. John Porco’s approach to this reassigned structure bears relations to his work on the similar natural product, panepophenanthrin.

This work hinges on the fact that both targets are actually dimeric; however, in the case of Hexacyclinol, a further cyclisation has occured to deliver the product. Thus, they created the monomer in four steps from the …

Still In The RBF »

[27 Jul 2006 | 9 Comments | 7,067 views]

Porco, Su, Lei, Bardhan and Rychnovsky. ACIEE, 2006, Early View. DOI: 10.1002/anie.200602854.
So the structure has been confirmed. And using a nice total synthesis too. So do we know if La Clair has lied? Not conclusively; someone would have to follow his synthesis exactly, and try to see where the discrepancies creep in [1]. However, it’s very difficult to see any element of honesty in his work, and what’s more annoying is why. Aferall, had he gone after the original target, completed the synthesis and then discovered that the spectral data …

Still In The RBF »

[25 Jul 2006 | 17 Comments | 12,902 views]

Boger, Ishikawa, Elliott, Velcicky and Choi. JACS, 2006,
ASAP. DOI: 10.1021/ja061256t.
More outstanding cyclisation action, this time from the Boger labs at Scripps. Working towards a whole class of bisindole alkaloid structures, including Vinblastine and vincristine (known for their potent anti-tumour action), they have completed
the total synthesis of vindoline (not a window cleaner). This structure, also found in nature, is a synthetic and biosynthetic precursor to the former targets. Along with an accompanying methodology paper, this work describes their forays into the synthesis of this interesting motif.

The work hinges upon an immense …

Meta »

[25 Jul 2006 | 2 Comments | 4,406 views]

As the more observant of you may have noticed, there’s a new navigation link above. That’s right, we’ve got Forums now! Yes, you now have your own place to rant about how great David Gin is, how James La Clair is a Bad Man, and how Corey invented the wheel. [1]
I’m not trying to step on Mitch’s feet (he’s doing a great job), we just need an area more attuned to the needs of the totally synthetic chemist. Somewhere where sarcasm, wit, great chemdraw skills and a complete inability to count quaternary centres [2] is …

Still In The RBF »

[24 Jul 2006 | 3 Comments | 4,235 views]

Boeckman, Shao, Wrobleski, Boehmler, Heintzelman, and Barbosa. JACS, 2006, ASAP. DOI: 10.1021/ja0581346.
An impressive synthesis of tetronolide in this JACS article, concerning this interesting spirotetronic acid type natural product. The biological activity of this target is particularly interesting, but I won’t go into it just now. Let’s just say this is an appealing target. Indeed, there have been other efforts towards it, including a total synthesis by Yoshii, and a formal by Roush.
Using a chiral auxiluary to derive much of the stereochemistry in the components, the first point of interest is …

Still In The RBF »

[20 Jul 2006 | 22 Comments | 6,841 views]

Gin, Eckelbarger and Wilmot. JACS, 2006, ASAP. DOI: 10.1021/ja063304f.
Ring expansion-action in this latest paper from David Gin, regarding the total synthesis of (-)-deoxyharringtonine, an anti-leukemia alkaloid. Starting from simple starting materials, they created the complex 7,5,5 system very quickly, using the ring-strain inherant in aziridines to open to a 7-member ring via a cyclisation.

This was then N-alkylated with Me3SiCH2I, which permited O-acylation with PivCl. The silyl group was then removed, generating a short-lived nonstabilized azomethine ylide. A stereo- and regioselective 1,3-dipolar cyclisation onto the PhSO2CH=CH2 led to the spiro-pyrrolidine. …

Still In The RBF »

[17 Jul 2006 | 9 Comments | 7,780 views]

Glorius, Heitbaum and Escher. ACIE, 2006, 45(29), 2732; DOI: 10.1002/anie.200504212.
Add, stir and filter! Frank Glorius, who gave a superb lecture at the OMCOS-13 last year, has written a great review of Asymmetric Heterogeneous Catalysis in Angewandte. I’ve been meaning to blog this for ages, but as it’s been a quiet few days, now couldn’t be a better time!

Still In The RBF »

[11 Jul 2006 | 8 Comments | 6,914 views]

Sasaki, Fuwa, and Ebine. JACS, 2006, ASAP. DOI: 10.1021/ja062524q.
Yup, another poly-ether, though with some interesting biological activity; this one seems to have positive effects, increasing tracheal mucus velocity, and thus potentially of use in respiritory disorders. Also, it appears to be a brevetoxin antagonist in vivo. As discussed in the comments surrounding the previous post (ciguatoxin), much of the work relating to ladder-type poly-ethers has been published before, so I’ll stick to the main disconnections.
Firstly, a Suzuki-Miyaura coupling of the main A,B and D,E fragments, building part of the C …

Still In The RBF »

[10 Jul 2006 | 27 Comments | 55,047 views]

Hirama, Inoue, Miyazaki, Ishihara, Tatami, Ohnuma, Kawada, Komano, Yamashita, Lee, and Masahiro . JACS, 2006, ASAP. DOI: 10.1021/ja063041p.
We’re back!! And with a tasty number to start the week with. Or rather not that tasty at all, what with the toxicity of this beast! Originally isolated from four metric tonnes of Moray Eels, at least the eels can breath a sigh of relief that Hirama et al. have finished their total synthesis of Ciguatoxin and its 51-HydroxyCTX3C analogue. Most of the ground work for this synthesis has been published already, including …