Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases.
To contact Derek email him directly: derekb.lowe@gmail.com
Twitter: Dereklowe
Here's a funny-looking compound for you - Ivorenolide A, isolated from mahogany tree bark, it has an 18-membered ring with conjugated acetylenes in it. That makes the 3-D structure quite weird; it's nearly flat. And it has biological activity, too (immunosuppression, as measured by T-cell and B-cell proliferation assay in vitro). Got anything that looks like this in your compound libraries? Me neither.
I read this paper yesterday. It has everything, isolation, elucidation of the structure, total synthesis of the compound, and biological results. My problem with it, is that the compound is not so potent, the synthesis has nothing special and is not considered biomimetic as they claim. Nothing really new derived from this paper, so why is it in JACS?
Who here thinks that %ee is bs? I know bromine has been used to enhance the ee of a CBS, historically; however, the alkyne has the Br pointed way far off into space if you draw the transition state out. I would argue that both side arms are of very similar steric bulk in the environment of the CBS catalyst.
10. mad dog on December 11, 2012 3:20 PM writes...
The structure has some of the features of the lipoxins, which are anti-inflammatory agents derived from the leukotriene pathway. Sort of a lipoxin macrocycle with immunosupressive activity.
I assumed that the epoxide is required. Eicosanoid and non-eicosanoid signalling contains a completely unreasonable amount of molecules that look a bit like that one. But they aren't cyclic. I guess this molecule could hit any number of enzymes and receptors in any mode.
1) "Biomimetic" seems like an overstatement - its probably an eicosanoid, so some of its biosynthesis might be known, but the key step doesn't look like anything an organism might use. Conformational constraint doesn't seem terribly biomimetic on its own.
2) An epoxide and two propargyl alcohols seems like an invitation to acid-catalyzed addition/cyclization heaven. Guess it'll be dosed IV?
This synthesis just doesn't seem really exciting to me.
13. Curt F. on December 11, 2012 10:20 PM writes...
@2: Nothing really new derived from this paper, so why is it in JACS?
I think you do the paper -- and the field of chemistry in general -- a disservice.
There isn't a whole lot of true discovery science left in chemistry. It's mostly all methods and applications. The chemistry of the natural world is one of those few places left where there's a lot of natural discovery to do. What molecules are there on Earth? In general, we don't know. This paper finds one more -- and one with several novel structural and chemical features: a macrocycle with conjugated alkynes. Isn't that a reason enough for the paper to be in JACS?
Curt F., I agree with you. If it's a cool new molecule, then it's cool chemistry. Otherwise, we will paint ourselves into a corner. If chemistry is to reassert itself as the central science, then we chemists have to broaden our perspectives and reconnect with other fields.
15. TheEdge on December 13, 2012 9:06 PM writes...
@Foolery: There are a number of reasons to grumble about this paper, but the CBS reduction probably isn't one of them. The difference between an alkyne and an olefin is significant enough to give good to excellent ee, even without the bromine. See the Evans Azaspiracid synthesis for one good example in TS (although that was a trans olefin).
The authors here clearly should have given some proof of ee, though.
1. JAB on December 11, 2012 12:23 PM writes...
After the enediyne antitumor antibiotics, nothing in the natural products world surprises me! Very cool...
Permalink to Comment2. S. on December 11, 2012 12:46 PM writes...
I read this paper yesterday. It has everything, isolation, elucidation of the structure, total synthesis of the compound, and biological results. My problem with it, is that the compound is not so potent, the synthesis has nothing special and is not considered biomimetic as they claim. Nothing really new derived from this paper, so why is it in JACS?
Permalink to Comment3. Sili on December 11, 2012 12:46 PM writes...
Finally something to do with those poly-yne compounds that don't work as molecular wires.
Permalink to Comment4. Foolery on December 11, 2012 1:04 PM writes...
Who here thinks that %ee is bs? I know bromine has been used to enhance the ee of a CBS, historically; however, the alkyne has the Br pointed way far off into space if you draw the transition state out. I would argue that both side arms are of very similar steric bulk in the environment of the CBS catalyst.
Permalink to Comment5. Foolery on December 11, 2012 1:10 PM writes...
Also, the ee is just magically reported in the supplemental! No chromatogram no nothing! What kind of journal is JACS turning into these days?
Permalink to Comment6. pgwu on December 11, 2012 2:16 PM writes...
Wonder if they analyzed Chinese mohagany tree as well. I like to eat the tree leaves of toona and curious what makes it taste so good.
Permalink to Comment7. gippgig on December 11, 2012 2:49 PM writes...
Mycomycin
Permalink to Comment8. DWJ on December 11, 2012 2:50 PM writes...
sigh...
Permalink to Commentanother worthless natural product synthesis.
We were doing the same 30 years ago
9. Sisyphus on December 11, 2012 3:02 PM writes...
The word "selective" has a whole spectrum of interpretations.
Permalink to Comment10. mad dog on December 11, 2012 3:20 PM writes...
The structure has some of the features of the lipoxins, which are anti-inflammatory agents derived from the leukotriene pathway. Sort of a lipoxin macrocycle with immunosupressive activity.
Permalink to Comment11. Morten G on December 11, 2012 3:50 PM writes...
mad dog is fairly right
Thromboxane A2
Hepoxilin A3
Epoxyeicosatrienoic acid
I assumed that the epoxide is required. Eicosanoid and non-eicosanoid signalling contains a completely unreasonable amount of molecules that look a bit like that one. But they aren't cyclic. I guess this molecule could hit any number of enzymes and receptors in any mode.
Permalink to Comment12. Hap on December 11, 2012 4:01 PM writes...
1) "Biomimetic" seems like an overstatement - its probably an eicosanoid, so some of its biosynthesis might be known, but the key step doesn't look like anything an organism might use. Conformational constraint doesn't seem terribly biomimetic on its own.
2) An epoxide and two propargyl alcohols seems like an invitation to acid-catalyzed addition/cyclization heaven. Guess it'll be dosed IV?
This synthesis just doesn't seem really exciting to me.
Permalink to Comment13. Curt F. on December 11, 2012 10:20 PM writes...
@2: Nothing really new derived from this paper, so why is it in JACS?
I think you do the paper -- and the field of chemistry in general -- a disservice.
There isn't a whole lot of true discovery science left in chemistry. It's mostly all methods and applications. The chemistry of the natural world is one of those few places left where there's a lot of natural discovery to do. What molecules are there on Earth? In general, we don't know. This paper finds one more -- and one with several novel structural and chemical features: a macrocycle with conjugated alkynes. Isn't that a reason enough for the paper to be in JACS?
Permalink to Comment14. hn on December 12, 2012 3:16 PM writes...
Curt F., I agree with you. If it's a cool new molecule, then it's cool chemistry. Otherwise, we will paint ourselves into a corner. If chemistry is to reassert itself as the central science, then we chemists have to broaden our perspectives and reconnect with other fields.
Permalink to Comment15. TheEdge on December 13, 2012 9:06 PM writes...
@Foolery: There are a number of reasons to grumble about this paper, but the CBS reduction probably isn't one of them. The difference between an alkyne and an olefin is significant enough to give good to excellent ee, even without the bromine. See the Evans Azaspiracid synthesis for one good example in TS (although that was a trans olefin).
Permalink to CommentThe authors here clearly should have given some proof of ee, though.