Talk:Vitamin B12 total synthesis

[Untitled]

I have been interested in the synthese of vitamin B12 for quite some time, and I happen to have access to all post-doc reports from both involved research groups, as well as to all the relevant ETH Ph.D. theses (now publicly accessible via the ETH e-collection). The chemistry described in this article is actually only one of two syntheses of vitamin B12, and I decided to put this in the greater context. Concerning the references (which I re-formatted in the standard Wiki format for journals and books), all publications (published lectures) by R.B. Woodward himself are now freely accessible, as well as one of the three publications by A. Eschenmoser. Easyloc (talk) 16:36, 7 July 2014 (UTC)

• Thanks! V8rik (talk) 21:12, 7 July 2014 (UTC)

Change to Present Tense

Per WP:TENSE the default verb tense for articles should be present tense. Past tense does apply to past events, and I recognize that this synthesis is not commonly done today. However, the process for B12 synthesis described is still valid and therefore subject to present tense. --Dag330 (talk) 00:08, 22 June 2018 (UTC)

Complete Revision

This is a complete, extended re-write of the original article; I started this with the consent of the original author v8rik, who encouraged me to go along with this MAJOR revision after sending him a first, incomplete draft of my version.

Notability: By time spent and manpower used, this is by far the largest synthesis to date, and the biggest collaborative project not only in organic synthesis until now (almost 50 years later), but in the entire life sciences before HUGO. It is, to my knowledge, the total synthesis most written about by third parties. This synthesis project is considered a major paradigm change in the total synthesis of natural products - but this can only be understood if BOTH synthetic approaches - Harvard/ETH, ETH, and the "joint final steps" common to both - are described at the same level. This is what I tried to do in this revision, as the original article described only ONE of the two concurrent, collaborative synthetic approaches to Vitamin B12 (mainly based on three freely accessible publications by R.B. Woodward who does not mention the other approach).

The way these approaches are linked and interrelated in what was a unique "competitive collaboration", ending in "joint final steps", IMHO does not permit a SEPARATE description of both approaches in two articles. I am perfecty aware of the fact that this now is an extremely LONG and COMPLEX article - for the latter, however, don't blame me, blame the molecule... To make it "palatable", I described in a more general way background and strategies of the two syntheses, and the outstanding international collaboration with no like precedents, no like successors so far. This "strategic information" should serve those readers well who only want to get a general idea about the essentials of this epochal project.

Details of both synthetic approaches and the "joint final steps" - the "tactics" - are given in the "hidden parts". These are presented - like in the original article for only one approach - using reaction schemes. This part has many links to Wikipedia articles about reaction types, compound classes, reagents, and (less common) solvents involved; i.e., individual steps in these complex syntheses may be referred to as special applications of these articles. I know that I made here an unusual (actually even discouraged !) application of the Show/Hide feature - but this was a VERY UNUSUAL total synthesis project! I evaluated the possibility of putting the details in separate articles, but the longer I considered that, the more I was convinced that such a ripping apart would do a disservice, both to the project and the readers - he/she can IMHO as easily IGNORE the details beyond the general parts as well as selectively and directly access them with Show/Hide for "tactics" (i.e., individual steps in the syntheses), and then jump back again for "strategies".

Length and complexity of the syntheses are also reflected in the number of sources cited (see also "The Publication Record" - another singularity in this project), and particularly their citation frequency which at first sight will look excessive. This was done to lead a reader as precisely as possible to the right spot (page numbers) in the very large volume of source material. There are several reasons for MULTIPLE citations to one fact: ETH and joint work is completely documented in theses - freely accessible, but voluminous, in German, and unusual as sources in chemical Wikipedia; thus, whenever appropriate, relevant journal articles were cited in addition. In his three published lectures, Woodward describes only the ETH/Harvard approach, including joint work as well as that done exclusively at Harvard or ETH, often without specific attribution; for the ETH part, also an Eschenmoser publication was cited ("neutral point of view"). In his full corrin synthesis papers (published more than 40 years after), Eschenmoser puts the syntheses in a larger and complete context for both approaches; both a source from the time of the actual project as well as a one of these recent corrin references were cited whenever deemed useful.

TECHNICAL POSTSCRIPTUM: For easier maintenance, all References and most Notes (i.e., references with additional comments, or explanatory remarks with or without references) are in separate lists, the references grouped by author/content separated by HTML comments. However, some - but strangely not all! - Notes containing also Refs had to be placed INLINE as their placement in the list led to a large undesirable whitespace in the display between Notes and References (or other rendering errors when the Notes list was placed after the References). Easyloc (talk) 20:11, 29 February 2020 (UTC)

Changes

Thanks to those Wikipedians who corrected my typos - after working for quite some time on a text, one tends to overlook them oneself... As far as links go, I corrected two changes which were certainly made with the best intention, but are unfortunately not correct/suitable:

1. meso ATOMS in tetrapyrroles refer to the CONSTITUTION of these compounds, they have nothing to do at all with the definition of meso COMPOUNDS, relating to their stereochemistry (CONFIGURATION)

2. when axial LIGANDS (with a metal-carbon bond) are discussed, a link to an article about cyclohexane conformation (axial SUBSTITUENTS, i.e. carbon-carbon bonds) IMHO is to far way off to be useful here. This prompted me to link now to "Coordination complex" - although this does not explicitly discuss axial ligands, it seems to me better suited than going back to no link at all. Easyloc (talk) 18:22, 21 March 2020 (UTC)

Monkbot: Refs

I'd like to thank Monkbot for cleaning up my Refs:

authorlink1 => author-link1 (lots of them, I copied that from old 2014 notes, should have checked HELP ...)

kicking out empty tags like issue=|

I'll try to remember that for next time

Easyloc (talk) 17:15, 12 December 2020 (UTC)

Vitamin B₁₂ structure

I replaced the "modelled" B₁₂ structure (Wikimedia Commons: Cyanocobalamin-3D-sticks.png) with a "real" structure from an x-ray crystal structure analysis (Dorothy Hodgkin, 1964; Wikimedia Commons: Vitamin_B12_hydrate.png). I did this not only because I consider determined structures preferable to modelled ones, but because the model contains several grave errors, particularly in the central chromophore, which is NOT a corrin at all: only ring B (top left) is a pyrroline ring (but with the position of its propionic side chain above instead below, and the acetic acid side chain shows a C-O instead a C=O group); "rings" C (top right), D (lower right), and A (lower left) are not 5-membered rings, each missing a bond; the configurations (up/down) of the side chain in "ring C", and of both methyl groups as well as the acetic acid side chain in "ring A" are all wrong; the Co-CN group is linear, not with an angle as shown. These errors are not that obvious in the picture size used in this article, but become more so when one enlarges the original from Wikimedia Commons.

With regards to the fact that this wrong vitamin-B₁₂ structure is used in more than 30 Wikipedia entries, I informed the author about my findings on his talk page, and I created a new talk page for its Commons entry with the relevant information. (This is the first time I came across such a problem; if I should have handled this differently, please let me know) Easyloc (talk) 11:41, 9 January 2021 (UTC)