IUPAC Nomenclature: SUCRALOSE

[BevillTheDevil]

http://www.rosalindfranklin.edu/cms/biochem/walters/sweet/sucralose.gif

How is this numbered (where to start numbering)?? what do the beta/alpha stand for?? I know the 6 memeberd ring is the galactopyranoside, is the 5 membered the fructo??

[qwnu]

IUPAC Nomenclature of Organic Chemistry (http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry)

[TomCowley]

Assuming you have some carbohydrate knowledge here-

The blue ring would be galactose (if Cl were replaced by OH), hence galactopyranoside. The red ring would be fructose.

In a normal aldose, carbon 1 is the aldehyde carbon. In a normal ketose, carbon 1 is the carbon on the end nearest the carbonyl carbon. In this disaccharide, each sugar unit is numbered individually. So on the blue ring, carbon 1 is the rightmost carbon, since it's the one that started as an aldehyde (and is now an acetal). Counting around, the Cl is obviously on carbon 4. Alpha means that the acetal linkage (the bond to the red O) is on the opposite side of the ring as Carbon 6. Since Carbon 6 is in the equatorial position, it's "on top" of the ring (the H there is axial-down), and the acetal linkage is on the bottom.

Looking at the red ring, the linked formerly-carbonyl carbon is C2, so the topmost carbon is C1, and the other Cl is on C6. This ring is beta because the ketal linkage is on the bottom of the ring, as is C6 (on the far right). Same side = beta.

[BevillTheDevil]

ty tom!! i was lookin particularly at the wikipedia picture for sucralose and they are missing a carbon...i was gettin really confused lol. The only thing im still somewhat confused w/ is the 4-deoxy, and the 1,6 dideoxy parts...

[TomCowley]

The deoxy is because the OHs that would be there in the sugar (galactose or fructose) aren't because they have been replaced by Cl. Deoxy: De - minus Oxy - Oxygen.

And yeah, the galactose ring is missing carbon 6 in the wikipedia structure, although the molecular model version appears correct at first glance.

[thesnowman22]

Threads like these make me glad I underacheived and became a PE teacher and basketball coach.