Talk:Isomalt

message: Judging from GeeJo's recent contributions, it appears someone had a bad run-in with Isomalt :) We could probably use some better sections for the content, as it's starting to get a bit long... Blueandwhiteg3 06:20, 3 February 2006 (UTC)

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thread_title: [[WP:FOOD|WikiProject Food and drink]] Tagging

message: I assume there is a difference between Isomalt and Isomaltose? The first being artificial and the second one a natural substance. Or are we talking about the same substance? itsme (talk) 13:39, 5 November 2009 (UTC)
replies: text: They're different structures. Isomalt is a sugar-ring attached to an alcohol chain, isomaltose is two sugar-rings attached to each other.  Looks like the difference is a -OH in place of an aldehyde groupPseudomonas(talk) 15:00, 5 November 2009 (UTC)
replies: text: According to the text in the article "isomalt is a disaccharide composed of the two sugars glucose and mannitol".  From the "Isomaltose"-article I can compose that isomaltose (like maltose) is formed from two units of glucose but with a α-(1-6)-linkage instead of the α-(1-4)-linkage. This would mean that they are both disaccharides, but one of the sugars is different (maltose instaed of glucose) itsme (talk) 15:36, 5 November 2009 (UTC)
thread_title:  Isomalt and Isomaltose

message: The structure shown in the article and the name ("1-O-α-D-Glucopyranosyl-D-mannitol") given in the infobox don't properly convey the fact that isomalt is not one structure, but a mixture of two. The article later says as much, but I don't feel confident enough to edit here. 
In fact, the article first says that isomalt is a mixture of 
:α-D-glucopyranosido-1,6-mannitol and α-D-glucopyranosido-1,6-sorbitol
and later it says that isomalt is a mixture of 
:6-O-α-D-glucopyranosido-D-sorbitol and 1-O-α-D-glucopyranosido-D-mannitol-dihydrate.
I don't know if this is a contradiction or just a difference in nomenclature. AxelBoldt (talk) 21:52, 21 April 2023 (UTC)
replies: text: @AxelBoldt I see that you are in the process of editing the article but, as you recognise, there are some pitfalls. This is an area where InChI and InChIKey become really helpful and I have checked these. It turns out that the best representation has Chemspider ID=2299218, which is at this URL found by InChIKey match. I checked that this is correct by using Biovia Draw. Note that the Chemspider image has 8 of its 9 stereocentres defined, with the ninth (the one produced as Isomaltulose is reduced) becoming a 50/50 mixture of the two possible configurations. There are various ways to name the individual components of the mixture but this is one on Chemspider and this is the other. Note the beauty of the InChI methodology: all these structures have SERLAGPUMNYUCK- as the first part of the key, with the stereochemistry encoded in the second part. I think it would be helpful for our article to include all the IDs and InChI etc., using the index_label parameters as described in  documentation. Are you familiar with that, or would you prefer that I did the edits needed? Mike Turnbull (talk) 10:49, 24 April 2023 (UTC)
replies: text: Thank you for looking into this. I'm not at all confident that what I did is correct; please make any changes you feel are helpful. In particular I didn't check the InChi. I'm also not clear on what the correct IUPAC names are. Then there is the issue that some sources give the GPS as a dihydrate and most don't. I also made several changes at Wikidata that probably should be checked. Cheers, AxelBoldt (talk) 12:18, 24 April 2023 (UTC)

text: I'm concerned that "8 of 9 stereocenters defined" is an adequate description. If isomalt is an exact 1:1 mixture of the two diastereomers, it's not "undefined" at that ninth stereocenter (some random diastereomeric mixture or uncertain identity). We'd need to encode both specific ones in the SMILES and other molecular descriptors ("A+B" not "undefined A vs B"). DMacks (talk) 15:10, 24 April 2023 (UTC)
replies: text: @DMacks @AxelBoldt I have updated the Chembox to reflect the situation as I see it. I agree that "undefined" is not the same as "1:1 mixture". That's one of the limitations of the way databases show stereochemistry. It is the difference between a substance and a sample. Samples can be 1:1 mixtures but substances are by (my) definition always a single entity. SMILES cannot represent samples which are in fact mixtures of two diastereoisomers, which is one of the reasons I prefer InChI. More later if you have questions.... Mike Turnbull (talk) 15:20, 24 April 2023 (UTC)
replies: text: I note that Chemspider also has ID=9789297, which shows isomalt as a 1:1 mixture of two fully-defined substances. We could use that for the main entry but I'm not sure this really helps! Mike Turnbull (talk) 15:38, 24 April 2023 (UTC)
replies: text: And from that Chemspider entry SMILES=O(C[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)CO)[C@H]1O[C@@H]([C@@H](O)[C@H](O)[C@H]1O)CO.OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO[C@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@H]1O does show two fully-defined substances as a 1:1 mixture if you want to use that to generate the image in JSmol. Mike Turnbull (talk) 15:43, 24 April 2023 (UTC)
replies: text: I was going to point out (ha!) that a 'point' is the delimiter for multicomponent SMILES. I don't know the InChI tech-specs. DMacks (talk) 15:52, 24 April 2023 (UTC)
replies: text: OK, Chemspider ID=9789297 links to the same literature as ID=2299218 but is clearer on the actual composition as a mixture. I think that's justification for using the former ID in the article and replacing the SMILES with the point-delimited version, which does then look correct when seen in JSmol. I'll do that now. Mike Turnbull (talk) 16:03, 24 April 2023 (UTC)
thread_title:  It is a mixture of two disaccharides, but which ones?