Showing posts with label LPU. Show all posts
Showing posts with label LPU. Show all posts

Friday, July 25, 2014

Déjà vu, LPU

Remember when I posted about the highly-similar cyclobutane insertion chemistry coming out of the Cramer group? Well, a new contestant has just been published in ACIEE:

Source: Cramer, ACIEE 2014

I jumped down the rabbit-hole of the Supporting Information, and returned with these two "general" procedures - blink, and you'll miss the differences!

Source: Cramer et. al., ACIEE 2014, February

Source: Cramer et. al., ACIEE, 2014, July

Same catalyst precursor. Same ligand (well, different enantiomer). Same solvent. Same time. Similar reaction temps and purification conditions. Now, I'm not saying that the Cramer group shouldn't have published this paper, but in the same journal? With essentially the same substrates?


Does anyone else believe that these could have been published together, in a single high-impact paper?

Thursday, February 13, 2014

Cyclobutanone Déjà vu

Didn't I just see that reaction? [rubs eyes]

From the laboratory of Prof. Nicolai Cramer (EPF Lausanne) comes some really neat examples of cyclobutanone C-C activation. Just mix with ~2 mol% of cationic Rh(I), and presto! Out comes a [3.1.2] bicyclo product reminiscent of several neuroactive natural products.

Oftentimes, a catalytic reaction will go gangbusters, but will stubbornly refuse all attempts at asymmetric induction. Apparently not so here - Cramer reports the asymmetric version in ACIEE about two weeks after the initial Organometallics report!

Angew. Chem. Int. Ed. 2014, ASAP
Organometallics 2014, ASAP
Honestly, I might never have noticed, except the TOC graphics for both are nearly identical: a comic pair of orange scissors "snipping" apart the cyclobutanone ring.

So, readers, what's your take? Can't wait to see this reaction applied to a challenging target? Or, a strange choice of synthetic "least publishable units" (LPUs)?

Tuesday, May 1, 2012

Same (Space) Science, Different (Dino) Day

"Five Acids" -  Duplicated in five papers
(PNAS, OLEB, IJC,  TL, JACS)
For those new to the Breslow #spacedino saga, Paul's collection of links back at ChemBark might be the best place to start. Long story short: a tongue-in-cheek press release proclaiming "Dinosaurs from Space!" drew much (unwanted) attention to a prebiotic homochirality review by Columbia University chemistry professor Ronald Breslow. Astute readers and blog commenters noted that the review text strikingly resembled that of earlier papers by the same author.

Well, just how similar were they? Not to incite a flame-war over "least publishable units" (LPUs), but, inspired by ChemBark's commentary on the matter, I've dug through the last six years of Breslow origin-of-life (OOL) publications, and summed up my findings below (Thanks to Paul, Stu, Chemjobber, Ash, Mark, Unity, Martyn, 'Anon,' and everyone else who provided source material for this post!)


"Transamination" - Duplicated in five papers
(TL, OL, OLEB,  IJC, JACS)
Over the last 6 years, I count nine papers that involve, in some fashion, the following topics: homochirality, prebiotic chemistry, enantiomeric amplification, meteorites, or OOL. Here's a list, with full titles, journals, and authorship:

2006Tet. Lett. - "Partial transfer of enantioselective chiralities from alpha-methylated amino acids, known to be of meteoric origin, into normal amino acids." Breslow, Levine
2006 - PNAS - "Amplification of enantiomeric concentrations under credible prebiotic conditions." Breslow, Levine
2008 - Org. Lett. - "Enantioselective Synthesis and Enantiomeric Amplification of Amino Acids under Prebiotic Conditions." Breslow, Levine
2009 - PNAS - "On the origin of terrestrial homochirality for nucleosides and amino acids." Breslow, Cheng
2010 - Org. Life Evol. Biosph. - "Imitating Prebiotic Homochirality on Earth." Breslow, Levine, Cheng
2010 - PNAS - "L-amino acids catalyze the formation of an excess of D-glyceraldehyde, and thus of other D sugars, under credible prebiotic conditions." Breslow, Cheng
2011 - Isr. J. Chem. - "Formation of L Amino Acids and D Sugars, and Amplification of their Enantioexcesses in Aqueous Solutions, under Simulated Prebiotic Conditions." Breslow
2011 - Tet. Lett. - "The origin of homochirality in amino acids and sugars on prebiotic earth." Breslow
2012 - JACS - "Evidence for the Likely Origin of Homochirality in Amino Acids, Sugars, and Nucleosides on Prebiotic Earth." Breslow

"Formose" - Duplicated in four papers
(OLEB, IJC, TL, JACS)
*So, for those keeping count at home, that's "Prebiotic" = 7, "Amino Acids" = 7, "Origin" = 4, "Chirality" = 4, "Sugars" = 4...and we're not yet past the titles!

(Throughout the post, I've also compared similar Figures, a task Paul and other bloggers had started tackling. I've examined each one in the context of the other eight.)

Poring over the text, many of the papers fall into similar thematic traps. First, Breslow poses a "big question" or concept (OOL, homochirality, etc.), then discusses the Murchison "carbonaceous chondritic meteorite." Breslow references the work of Cronin and Pizzarello, and discusses circularly polarized light, white dwarf stars, and synchrotron radiation. The Breslow "formose reaction" paper (Tet. Lett., 1959, 22-26) sets the stage for the D sugars, and the group's transamination / amplification work for the L-AA papers.

"Nucleosides" - Duplicated in five papers
(TL, OLEB, IJC, PNAS, JACS)
Dead-center in the most recent four papers (OLEB, TL, IJC, JACS), one finds the Morowitz equation, which explains enantiomeric amplification from tiny initial excesses of single enantiomers. Unfortunately, one also finds the most glaring piece of self-plagiarism: the kinetics paragraph. As noted by Stuart Cantrill and several others, full pages are duped among the separate articles - TL p. 4229 is identical to JACS p. 5-6, IJC from 992-993, and (almost) OELB from 20-21.

Even the dinosaur joke, that witty aside that brought all the attention to the paper in the first place, was repeated three times! (IJC, TL, JACS). This inclusion almost begs the question . . .did Breslow wish to be caught?

Obligatory dinosaur image
Source: stegosaurus.com
Nonetheless, the offending paper has been removed from the JACS website, and further editorial action likely awaits him. I remain puzzled, however. How could an academic legend, a chemical pioneer, a man whose research has launched quite a few stelllar professorships (Gellman, Schepartz, Groves, Grubbs, among others), simply reissue the same science, over and over again, in different journals? Breslow continually mentions "credible" conditions; was this because the papers were less so? There's also the puzzling publication order, from 'worst to first.' Breslow re-publishes tenuous material from TL (Impact Factor = 2.6) in JACS (I.F. = 9.0), where visibility no doubt increases? Generally, high-impact research starts out in high-impact journals, and later trickles down.

Time will tell what will happen to the #spacedino paper. My final hope would be that aspiring academics and graduate students watch the situation unfold, and take care against any similar publishing behavior.