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Carbohydrate Nomenclature Worksheet KEY CHEM 8B, UCSC, Binder 1. Draw one example of each of the following types of monosaccharides (there may be several correct answers) and indicate the number of possible stereoisomers while keeping the same D/L configuration. (a) D-Aldotriose (c) L-Ketotetrose (b) L-Aldotriose CHO H OH CH2OH CHO HO H CH2OH 1 possible 1 possible CH2OH C O HO H CH2OH 1 possible 4 possible (d) L-Aldopentose CHO CHO CHO HO H H OH H OH H OH HO H H OH HO H HO H HO H CH CH2OH CH2OH 2OH CHO HO H HO H HO H CH2OH (e) D-Ketohexose 4 possible CH OH CH2OH CH2OH 2 C O C O C O H OH H OH HO H H H OH HO H OH H OH H OH H OH CH OH CH2OH CH2OH 2 (f) L-Aldohexose H H H HO CHO OH OH OH H CH2OH H H HO HO CHO OH OH H H CH2OH H HO H HO CHO OH H OH H CH2OH H HO HO HO CH2OH C O HO H HO H H OH CH2OH ANY ONE EXAMPLE IS CORRECT FOR (d), (e), & (f). I WOULDN'T EXPECT YOU TO DRAW ALL STEREOISOMERS ON AN EXAM! 8 possible CHO CHO CHO OH HO H HO H H H OH H OH H H OH HO H H HO H HO H CH2OH CH2OH CH2OH HO HO H HO CHO H H OH H CH2OH HO HO HO HO CHO H H H H CH2OH 2. What is the relationship between the following monosaccarides (enantiomers, diastereomers, or epimers)? You’ll find the structures of D-monosaccharides in chapter 25. You should be able to figure out the structures of the corresponding L-monosaccharides if you’re paying attention to the reading! The only monosaccharide you’re expected to memorize for exams is D-glucose. a. b. c. d. D-glucose and L-glucose ARE ENANTIOMERS D-glucose and D-allose ARE C3 EPIMERS (more specific than diastereomers) D-allose and D-altrose ARE C3 EPIMERS (more specific than diastereomers) D-altrose and D-glucose ARE DIASTEREOMERS (more than one chiral center is different) e. D-glucose and D-mannose ARE C2 EPIMERS (more specific than diastereomers) f. L-glucose and D-idose ARE C5 EPIMERS (more specific than diastereomers) Carbohydrate Nomenclature Worksheet KEY CHEM 8B, UCSC, Binder 3. Fischer projections of D-glucose’s epimers D-Glucose H HO H H CHO OH H OH OH CH2OH CHO H H OH OH CH2OH C2 epimer HO HO H H CHO OH OH OH OH CH2OH C3 epimer H H H H CHO OH H H OH CH2OH C4 epimer H HO HO H 4. Monosaccharides can act as nucleophiles and/or electrophiles. Redraw any sugar from #1d and #1e and indicate the functional groups that could act as nucleophiles and those that can serve as electrophiles. alcohol = nucleophile aldehyde = electrophile CHO H OH H OH 4 alcohols = nucleophiles HO H CH2OH CH2OH C O ketone = electrophile H OH H OH 4 alcohols = nucleophiles H OH CH2OH 5. Redraw the following structures exactly. These are the backbone structures to be used for #6 of this worksheet. Pay special attention to the placement of the oxygen and the particular chair conformation used (no ring flips necessary!). O Haworth projection O Chair conformation (NO KEY SHOULD BE NECESSARY!) 6. Draw Haworth projections and the chair conformation for the following aldohexoses using the backbone structures from #5. Consult Fig 25.3 of McMurry; memorize the structure of DGlucose for the final exam. Left or right side on Fischer projection If it were LEFT UP to me, I'd be DOWN RIGHT angry * works for C2 through C4 * Pointing up or down on the ring (Haworth or chair) Carbohydrate Nomenclature Worksheet KEY (a) CHEM 8B, UCSC, Binder Chair Haworth The C5 CH2OH (penultimate) group always points "up" for D-sugars Bonds in Haworth projections are HO up/down only, no axial or equatorial, no wedge/dash 4 1 CHO H 2 OH H 3 OH H 4 OH H 5 OH 6 CH 2OH 6 OH C1-C4 are "down" but alternate axial-equatorial. 5 O 5 Take special note of the HO 1 2 angles of the equatorial 2 1 3 HO 3 OH groups - parallel to bonds OH in the ring. OH OH OH OH C1 OH (anomeric) points "down" for alpha (α) D-Allose O 6 4 α-D-Allopyranose (b) HO 6 OH O OH 5 4 2 2 3 O 5 HO 1 HO 6 4 3 OH OH 1 OH OH OH Everything except C1 is the same as part (a) β-D-Allopyranose (c) 1 HO CHO H OH 3 HO H H 4 OH H 5 OH 6 CH 2OH 6 OH 2 5 4 O 4 2 HO HO 1 OH HO 3 OH 6 O 5 2 OH 3 OH 1 OH Everything except C3 is the same as part (a) α-D-Glucopyranose D-Glucose (d) HO 6 OH O OH 5 4 1 OH 2 HO 6 4 HO HO 2 OH OH 3 3 Hey, look at that! They're all equatorial! Notice that equatorial bond angles still point up or down, not horizontally O 5 1 OH Everything except C1 is the same as part (c) β-D-Glucopyranose (e) 1 CHO 2 HO H H 3 OH HO 4 H H 5 OH 6 CH 2OH D-Idose (f) HO HO OH OH 6 O 5 4 3 4 OH1 OH 2 OH 6 5 3 O OH 2 OH C2 and C4 differ from part (a) α-D-Idopyranose HO 6 HO 5 4 OH OH 6 O OH4 5 1 HO 3 1 OH 2 OH 3 O OH 2 OH 1 OH Everything except C1 is the same as part (e) α-D-Idopyranose