Comments on: Diazonamide A http://totallysynthetic.com/blog/?p=773 4,512 Ph. D. students died to make this blog... Mon, 06 Sep 2010 21:36:02 -0600 hourly 1 http://wordpress.org/?v=3.0 By: todays http://totallysynthetic.com/blog/?p=773&cpage=1#comment-179432 todays Wed, 19 Nov 2008 07:32:55 +0000 http://totallysynthetic.com/blog/?p=773#comment-179432 Hey where did you find the information in your post? Hey where did you find the information in your post?

]]> By: Mike http://totallysynthetic.com/blog/?p=773&cpage=1#comment-61336 Mike Sun, 30 Sep 2007 19:20:24 +0000 http://totallysynthetic.com/blog/?p=773#comment-61336 You've got to love reference 16 in this paper: Bould, L. Studies on the synthesis of tetracycline. Ph.D. Thesis; Imperial College, London, 1968; pp 91 and 153 [...] In 1968, Magnus was a Ph.D. student working next to Bould, and as a consequence knew about the transformation of 56 into 57. This information initiated the notion (36 years later!) that this type of reaction could be used for the construction of the C-10 quaternary center in diazonamide A. So take note of what your co-workers are doing... you never know when it might come in useful! You’ve got to love reference 16 in this paper:

Bould, L. Studies on the synthesis of tetracycline. Ph.D. Thesis; Imperial
College, London, 1968; pp 91 and 153 [...] In 1968, Magnus was a
Ph.D. student working next to Bould, and as a consequence knew about
the transformation of 56 into 57. This information initiated the notion (36
years later!) that this type of reaction could be used for the construction of
the C-10 quaternary center in diazonamide A.

So take note of what your co-workers are doing… you never know when it might come in useful!

]]> By: BMChem http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60932 BMChem Wed, 26 Sep 2007 21:22:20 +0000 http://totallysynthetic.com/blog/?p=773#comment-60932 I'm not sure I care for the title of this paper so much. A "powerful" stereoselective migration... What exactly is a powerful migration? How powerful is it? Can it lift a truck? Anybody? I’m not sure I care for the title of this paper so much. A “powerful” stereoselective migration…

What exactly is a powerful migration? How powerful is it? Can it lift a truck?

Anybody?

]]> By: milkshake http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60888 milkshake Wed, 26 Sep 2007 06:01:12 +0000 http://totallysynthetic.com/blog/?p=773#comment-60888 SOCl2 gives products of SNi with secondary alcohols only in absence of base (like pyridine). The effect of base is that enough Cl(-) stays in the solution so that the substitution goes usually with inversion. Tertiary alcohols are supposed to go by SN1 except that in this particular case of alpha carbonyl and oxazol in alpha position the carbocation is destabilised so one should expect situation similar to the case of secondary alcohol. SOCl2 gives products of SNi with secondary alcohols only in absence of base (like pyridine). The effect of base is that enough Cl(-) stays in the solution so that the substitution goes usually with inversion.

Tertiary alcohols are supposed to go by SN1 except that in this particular case of alpha carbonyl and oxazol in alpha position the carbocation is destabilised so one should expect situation similar to the case of secondary alcohol.

]]> By: diketene http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60812 diketene Tue, 25 Sep 2007 17:13:57 +0000 http://totallysynthetic.com/blog/?p=773#comment-60812 Totallysynthetic got a face lift. But it looks uglier... Totallysynthetic got a face lift. But it looks uglier…

]]> By: ChemSpiderMan http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60647 ChemSpiderMan Mon, 24 Sep 2007 05:07:57 +0000 http://totallysynthetic.com/blog/?p=773#comment-60647 Paul...I've spent some time tonight looking more deeply into the chemical structure details especially. I made a couple of posts about this this evening...one before seeing PMRs post above and one afterwards. Your readers especially should be interested in the ChemRefer service I talk about to search publications online. http://www.chemspider.com/blog/?p=147 and http://www.chemspider.com/blog/?p=153 This has given me an interesting opportunity to validate structures across databases. Can you do me a favor and send me the chemical structure you drew in ChemDraw? Thanks. Paul…I’ve spent some time tonight looking more deeply into the chemical structure details especially. I made a couple of posts about this this evening…one before seeing PMRs post above and one afterwards. Your readers especially should be interested in the ChemRefer service I talk about to search publications online.

http://www.chemspider.com/blog/?p=147
and
http://www.chemspider.com/blog/?p=153

This has given me an interesting opportunity to validate structures across databases. Can you do me a favor and send me the chemical structure you drew in ChemDraw? Thanks.

]]> By: ChemSpider Blog » Blog Archive » More Comments About Diazonamide A - other efforts to distinguish WHAT’S REAL? http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60646 ChemSpider Blog » Blog Archive » More Comments About Diazonamide A - other efforts to distinguish WHAT’S REAL? Mon, 24 Sep 2007 05:06:20 +0000 http://totallysynthetic.com/blog/?p=773#comment-60646 [...] Following on from my posting last night about Diazonamide A I note that PMR has blogged about this. Peter’s conclusion was that “the blogosphere is starting to emerge as a serious place to look for chemistry.” I have to agree! Just Paul’s one posting on Diazonamide A has resulted in a lot of additional trackbacks! [...] [...] Following on from my posting last night about Diazonamide A I note that PMR has blogged about this. Peter’s conclusion was that “the blogosphere is starting to emerge as a serious place to look for chemistry.” I have to agree! Just Paul’s one posting on Diazonamide A has resulted in a lot of additional trackbacks! [...]

]]> By: ChemSpider Blog » Blog Archive » Diazonamide A and Chats with TotallySynthetic.Com http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60634 ChemSpider Blog » Blog Archive » Diazonamide A and Chats with TotallySynthetic.Com Mon, 24 Sep 2007 03:11:32 +0000 http://totallysynthetic.com/blog/?p=773#comment-60634 [...] As discussed in an earlier blog I spent some time chatting with Paul Doherty and Peter Murray Rust this weekend…specifically around InChIs and InChIKeys. I’d originally suggested to Paul that he put InChIs on the site so that I could use them to check for presence of the structures he draws in the ChemSpider database. Well, now he’s started to include them on his postings I get to check them. [...] [...] As discussed in an earlier blog I spent some time chatting with Paul Doherty and Peter Murray Rust this weekend…specifically around InChIs and InChIKeys. I’d originally suggested to Paul that he put InChIs on the site so that I could use them to check for presence of the structures he draws in the ChemSpider database. Well, now he’s started to include them on his postings I get to check them. [...]

]]> By: Unilever Centre for Molecular Informatics, Cambridge - petermr’s blog » Blog Archive » Finding chemical structures - InChIs et al., an amusement http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60580 Unilever Centre for Molecular Informatics, Cambridge - petermr’s blog » Blog Archive » Finding chemical structures - InChIs et al., an amusement Sun, 23 Sep 2007 18:11:02 +0000 http://totallysynthetic.com/blog/?p=773#comment-60580 [...] Totally Synthetic, Chemspider and I have been discussing the value of InChIs in blogs. TS’s blog is, of course Openly available under CC licence, and he is widely revered in the community for the beauty and acuuracy of his structural diagrams. This post is a slightly light-hearted voyage through what can be discovered with Toll-Access barriers in place. I leave readers to judge whether TSand Pubmed are up to the ease and value of the information from commercial providers. I’m reading this from outside the University and I do not have a VPN. This is useful as it shows me what it’s like to be an information-impoverished reader. TS blogged today about Diazonamide A , a natural product which was billed as the next big breakthrough in cancer some years ago. (It has 4 reports in Pubmed about its biology, and 26 ones about the chemical synthesis. Taxol has 30,000). Anyway TS has taken the advice of the Blue Obelisk list and managed to put InChIs into his blog. [...] [...] Totally Synthetic, Chemspider and I have been discussing the value of InChIs in blogs. TS’s blog is, of course Openly available under CC licence, and he is widely revered in the community for the beauty and acuuracy of his structural diagrams. This post is a slightly light-hearted voyage through what can be discovered with Toll-Access barriers in place. I leave readers to judge whether TSand Pubmed are up to the ease and value of the information from commercial providers. I’m reading this from outside the University and I do not have a VPN. This is useful as it shows me what it’s like to be an information-impoverished reader. TS blogged today about Diazonamide A , a natural product which was billed as the next big breakthrough in cancer some years ago. (It has 4 reports in Pubmed about its biology, and 26 ones about the chemical synthesis. Taxol has 30,000). Anyway TS has taken the advice of the Blue Obelisk list and managed to put InChIs into his blog. [...]

]]> By: ChemSpiderMan http://totallysynthetic.com/blog/?p=773&cpage=1#comment-60487 ChemSpiderMan Sun, 23 Sep 2007 01:10:22 +0000 http://totallysynthetic.com/blog/?p=773#comment-60487 I checked the 6 structures in more detail...we have a dereplication issue it appears...this resolves a couple of the structures. The other issues are differences in stereochemistry. You might want to check the explicit stereochemistry...notice the ? in the InCHI for 39? below InChI=1/C40H34Cl2N6O6/c1-15(2)27-37-46-29-32(54-37)40-20-9-5-8-19(18-7-6-10-22-25(18)26(33(41)43-22)31-34(42)48-38(29)53-31)28(20)47-39(40)52-24-12-11-17(13-21(24)40)14-23(35(50)45-27)44-36(51)30(49)16(3)4/h5-13,15-16,23,27,30,39,43,47,49H,14H2,1-4H3,(H,44,51)(H,45,50)/t23-,27-,30-,39?,40-/m0/s1 I checked the 6 structures in more detail…we have a dereplication issue it appears…this resolves a couple of the structures. The other issues are differences in stereochemistry. You might want to check the explicit stereochemistry…notice the ? in the InCHI for 39? below

InChI=1/C40H34Cl2N6O6/c1-15(2)27-37-46-29-32(54-37)40-20-9-5-8-19(18-7-6-10-22-25(18)26(33(41)43-22)31-34(42)48-38(29)53-31)28(20)47-39(40)52-24-12-11-17(13-21(24)40)14-23(35(50)45-27)44-36(51)30(49)16(3)4/h5-13,15-16,23,27,30,39,43,47,49H,14H2,1-4H3,(H,44,51)(H,45,50)/t23-,27-,30-,39?,40-/m0/s1

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