Koreeda+-Chap14-2 - - Chem 215 F10 Notes Dr. Masato Koreeda...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 215 F10 Notes - Dr. Masato Koreeda - Page 1 of 9. Chapters 14.8r23-L,2,5, and 7: Carbohydrates Part II II. Glycosides - A general term used to describe organic molecules covalently bound to carbohydrate molecules ( *E,El'through anomeric bonds). (1) Formation of glycosides CH3OH, 0.7 Vo HCl,10 'C (short time) 6cHroH Ho-l-H u -l ou^ H'r' ']!-A;anomericcarbon HHO )mer methyl a-D- gl ucofuranoside methyl o-o-glucopyranoside Date: October 22,2010 HHO p-anomer methy p-o- glucofuranoside HO HO oH^ H ?cH' -1zt'r-;-l/,anomericcarbon HO--r Ho-1+to\, + nO-lztlr- , Hb AJ.unot.ric carbon MAJOR PRODUCT q,-anomer -66% MrNoR PRODUCT B-anomer methyl p-l- glucopyranoside In general, (5-membered) furanosides are formed preferentially under the kinetic conditions, whereas (6-membered) pyranosides are formed under the thermodynamic conditions, i.e., more stable. Five membered systems have a number of eclipsing interactions, thus less stable. C1 -epimers; anomers; diastereomers HO-o t\ Ho-i*or, nO.-Lztrr : ,rX | \ anomeric carbon HO\ *o,.;od*?o' Hb \ anomeric carbon *-anomer Ho dt CH3OH,4VoHCl,rt
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chem 215 F10 Notes - Dr. Masato Koreeda - Page 2 of 9 ' (2) Mechanism for the formation of anomeric glycosides Date: October 22,2010 When protonation occurs on the anometic OH. oH- anomeric carbon HO HO B-anomer H gJ, lone pair-assisted\ lonlzatlon. \ HO HO 1 H ..1 r+l Hr-O:CH3 mixture H I : O-CH3 ( H HO H I ; O-CH3 t H ^l-> -t), HO HO \ HO Hoil HO- \ Ho--Tlor H HoJfy." a-anomer to A"n. HO HO p-anomer Comments'. . The c-anomeric hemiacetal undergoes similar processes to produce a mixture of anomeric glycosides. the anomeric (i.o., Cr . protonation on the lone pairs of the oxygen atoms other than the anomeric (i.e., Ur-u) i ether ring oxygen ones dies not lead to the ready elimination of the protonated hydroxyl HO.-6 4J-o 5) \ pair-assisted ionization. When protonation occurs on the ether oxygen atom. lone pair-assisted ionization. - HO HO Hoil rotation along the Ct-C, bond ocH3 o-cH3 o-H \HO J- IJ \,y'-\ 'r' * / :O-CH, \ \ 'i. HO
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 9

Koreeda+-Chap14-2 - - Chem 215 F10 Notes Dr. Masato Koreeda...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online