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Carbohydrate Nomenclature Worksheet KEY CHEM 8B, UCSC, Binder

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Carbohydrate Nomenclature Worksheet KEY CHEM 8B, UCSC, Binder 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 (b) L-Aldotriose (c) L-Ketotetrose CHO CHO CH2OH H OH HO H C O CH2OH CH2OH HO H 1 possible 1 possible CH2OH 1 possible (d) L-Aldopentose 4 possible CHO CHO CHO CHO H OH H OH HO H HO H H OH HO H H OH HO H HO H HO H HO H HO H CH2OH CH2OH CH2OH CH2OH (e) D-Ketohexose ANY ONE EXAMPLE IS CORRECT 4 possible FOR (d), (e), & (f). CH2OH I WOULDN'T EXPECT YOU TO CH2OH CH2OH CH2OH C O DRAW ALL STEREOISOMERS C O C O C O ON AN EXAM! H OH H OH HO H HO H H OH HO H H OH HO H H OH H OH H OH H OH CH OH CH2OH 2 CH2OH CH OH 2 (f) L-Aldohexose 8 possible CHO CHO CHO CHO CHO CHO CHO CHO H OH H OH H OH H OH HO H HO H HO H HO H H OH H OH HO H HO H H OH H OH HO H HO H H OH HO H H OH HO H H OH HO H H OH HO H HO H HO H HO H HO H HO H HO H HO H HO H CH2OH CH2OH CH2OH CH2OH CH2OH CH2OH CH2OH 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. D-glucose and L-glucose ARE ENANTIOMERS b. D-glucose and D-allose ARE C3 EPIMERS (more specific than diastereomers) c. D-allose and D-altrose ARE C2 EPIMERS (more specific than diastereomers) d. 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 CHO CHO CHO CHO H OH HO H H OH H OH HO H HO H H OH HO H H OH H OH H OH HO H H OH H OH H OH H OH CH OH CH2OH CH2OH CH2OH 2 C3 epimer C4 epimer C2 epimer 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 CH2OH CHO C O ketone = electrophile H OH H OH H OH 4 alcohols = nucleophiles H OH 4 alcohols = nucleophiles HO H H OH CH OH 2 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 O Haworth Chair projection 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 D- Glucose 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 CHEM 8B, UCSC, Binder (a) Haworth Chair The C5 CH2OH (penultimate) group always points "up" for D-sugars 1 Bonds in Haworth CHO projections are HO 6 OH H 2 OH up/down only, C1-C4 are "down" but 6 3 O 4 alternate axial-equatorial. H OH no axial or equatorial, 5 5 O no wedge/dash 4 1 HO Take special note of the H 4 OH 2 angles of the equatorial HO 3 2 OH 3 1 H 5 OH OH groups - parallel to bonds OH OH OH OH in the ring. 6CH OH 2 C1 OH (anomeric) points "down" for alpha (α) D-Allose α-D-Allopyranose (b) HO 6 OH O OH 4 6 5 5 O 4 1 HO 2 OH 3 2 3 HO OH 1 OH OH OH Everything except C1 is the same as part (a) β-D-Allopyranose (c) 1 CHO HO 6 OH 2 H OH O 4 6 5 O 3 5 4 1 HO HO H OH 2 H 4 OH 2 HO 1 HO OH 3 5 3 OH H OH OH OH 6CH2OH Everything except C3 is the same as part (a) D-Glucose α-D-Glucopyranose (d) HO 6 OH Hey, look at that! O OH 4 6 5 5 O They're all equatorial! 4 1 HO OH 2 Notice that equatorial OH 2 HO bond angles still point HO 1 3 3 OH up or down, not OH horizontally Everything except C1 is the same as part (c) β-D-Glucopyranose (e) (f) 1 HO OH HO OH CHO 6 OH 6 OH 6 6 2 HO O O HO H 5 4 5 O HO 5 OH4 5 O 3 1 OH 1 OH H OH 4 OH 4 HO HO 4 H 3 OH 3 OH 2 3 2 1 2 3 2 H 5 OH OH OH 1 OH OH OH 6CH2OH D-Idose C2 and C4 differ from part (a) Everything except C1 is the same as part (e) -D-Idopyranose α α-D-Idopyranose .
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