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Discussion Carbohydrates. Nomenclature. (D)-glucose. α-pyranose form: α-(D)-glucopyranose. (2 R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal. Dextrose. Hawthorne structure α-pyranose form: α -(D)-glucose. β-pyranose form: β-(D)-glucopyranose. Another Chiral sugar: Erythrose. - PowerPoint PPT Presentation

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Discussion Carbohydrates

Discussion CarbohydratesNomenclature(D)-glucose(2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanalDextrose-pyranose form:-(D)-glucopyranose

-pyranose form:-(D)-glucopyranoseHawthorne structure-pyranose form:-(D)-glucose

Another Chiral sugar: ErythroseHow do you convert to a regular zig-zag structure? Three ways:1) use models2) determine R or S configurations, draw a four carbon chain and draw substituents then re-check configurations3) Draw intermediate structures and rotate molecule and bonds to get into zig-zagMethod 2:Method 3: By drawing & rotatingTakes time, can make mistakes and you still should check the configurations (R or S) at the endDraw the enantiomer of erythroseDraw the enantiomer of erythroseYou are switching two groups involves breaking and making two bonds to interconvert each center (Four bonds total)Draw the diastereomers of the erythrose isomers shownTo create diastereomers1) first figure out how many total possible diastereomers ( = 2n, n = # chiral carbons). There are 22 = 4 diastereomers possible (two pair of enantiomers)2) then switch two groups to just one of the chiral centers to form one diastereomer.3) then draw its mirror image as above.Meso compoundsFound among diastereomers of molecules with plane of symmetry between two (or four, six, eight ) chiral centers.

With this plane of symmetry the RS & SR enantiomers are not enantiomers but are superimposable. These are achiral and will not show optical activity.

Meso is an issue with stereoselective reactions (syn or trans) to symmetrical olefinsTo generate 1,2-dihalides, 1,2-diols, epoxides or cyclopropanesFor example:[1] If the ring closes on a hydroxyl which is on the right in the Fischer projection, the hydroxymethyl group (tail) points up; if it closes on a hydroxyl which was on the left in the Fischer projection, the tail points down.[2] The ring hydroxyls point down if they are on the right in the Fischer projection, and up if they are on the left in the Fischer projection. (Note that these are also the positions they are in after the Fischer projection has been rotated 90 clockwise to lie on its side.)[3] The hydroxyl on the anomeric carbon points down in the D series if it is and up if In the L series, is up and is downNomenclature?Nomenclature(D)-fructose-(D)-fructofuranose(2S,3S,4S,5R)-2,5-bis(hydroxymethyl)tetrahydrofuran-2,3,4-triol(2S,3S,4S,5R)-2,5-bis(hydroxymethyl)tetrahydrofuran-2,3,4-triolRRSSRSSNomenclature(D)-fructoseSucroseFisher ProjectionsEpimersOptically activeOptically activeC2 epimersC2 epimers

C2 epimers

HNO3Mirror image is same compoundOptically activeOne segment of Fischer Proof

OOH OHOH

OH

OH

(2S,3R,4S,5S,6R)-6-(hydroxymethyl)tetrahydro-2H-pyran-2,3,4,5-tetraol

OOH

OH

OH

OHHO

CHOOHHHHOOHHOHH

CH2OH

R

RR

S

OH

HO

H

HO

H

HOOHH

H

OH

OH

HO

H

HO

H

HOHH

OH

OH

CHO

OHH

HHO

OHH

OHH

CH2OH

(2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

C

OH

C

H

C

OH

HO H

C

OH 1

C

H

C

OH

HO H

O

1 + 6 + 8 = 15

8 + 8 + 1 = 17

6

6

8

C 2

OH1

C 3H

C

OH

HO H

Counterclockwise, But hydrogen is pointing at you, no into the boardSo the order is really clockwise and the chiral center is"R"

CHO

OHH

OHH

CH2OH

CHO

OHH

OHH

CH2OH

R

R

Draw four carbon zig-zag structure:

OHCCH2OH

HO

OH

check configurations OHC 2 CH2OH

3

HO

OH1

Hydrogen in back, counter clockwise:opps, its S

OHC CH2OHHO

OH So invert at that center OHC2 3 CH2OH

HO1

OHR It's R OHC

CH2OHHO

OH

(2R,3R)-2,3,4-trihydroxybutanalCheck configuration at second carbon

(2R,3R)-2,3,4-trihydroxybutanal

CHO1

2 OHH3 OHH

CH2OH4

CHO

OHH

OHH

CH2OH

OHC

OH

H

OH

H

CH2OHOHC CH2OH

HO OHH H

(2R,3R)-2,3,4-trihydroxybutanal

(2R,3R)-2,3,4-trihydroxybutanal

OHC CH2OH

HO OHH H OHC

1

23

CH2OH4H

OH

HO

H

CHO

OHH

OHH

CH2OH

CHO

HO H

HO H

CH2OH

CHO

OHH

OHH

CH2OH

CHO

HO H

HO H

CH2OH

CHO

OHH

OHH

CH2OH

CHO

HO H

HO H

CH2OH

CHO

OHH

OHH

CH2OH

(2R,3R)-2,3,4-trihydroxybutanal (2S,3S)-2,3,4-trihydroxybutanal

CHO

OHH

HHO

CH2OH

switched these two

CHO

HO H

H OH

CH2OH

(2R,3S)-2,3,4-trihydroxybutanal (2S,3R)-2,3,4-trihydroxybutanal

R

S

S

R

R

R

S

S

CH2OH

OHH

OHH

CH2OH

CH2OH

HO H

HO H

CH2OH

CH2OH

OHH

OHH

CH2OH

(2R,3S)-butane-1,2,3,4-tetraol (2R,3S)-butane-1,2,3,4-tetraol

CH2OH

OHH

HHO

CH2OH

CH2OH

HO H

H OH

CH2OH

(2S,3S)-butane-1,2,3,4-tetraol (2R,3R)-butane-1,2,3,4-tetraol

S

S

R

R

S

R

R

S

SAME!!! or Meso

These are enantiomers

OsO42) NaHSO4

H2O

OH

OHH

HOH

OHH

H+

OsO42) NaHSO4

H2O

OH

OHH

HOH

OHH

H+

(2R,3R)-butane-2,3-diol (2S,3S)-butane-2,3-diol

Enantiomers

(2R,3S)-butane-2,3-diol (2R,3S)-butane-2,3-diol

Meso- achiral

OOH OHOH

OH

OH

CHOOH

H

H

OH

OH

H

OH

HHOH2C

CHOOHHHHOOHHOHH

CH2OH

OHHCCOH

COH

COH

C

O

CHO

CHOOHHHHOOHHOHH

CH2OH

R

RR

S

CC OHHC HHOC OHHC OHCH2OH

HHO

OOH

HOOH

OHOH

(3S,4R,5R)-1,3,4,5,6-pentahydroxyhexan-2-one

OHHHO H

H OHO

HO OH

OH

OH

OH

OHHO

OR R S

OHHHO H

H HOO

HO OH

S

SR

R

Cahn-Ingolg-Prelogrules indicate it should be S,S,R,R

OH

C

H

C

HO H

H CCC

HOO

HO OHH H

OCC

O

H

CH

OCO

H

C

HO

CO

1

23

H

H

H

OH

OH

OH

OHHO

O

CH2OHOHHOOHHOHH

CH2OH

OH

HOH

H

H

HOO

HO

HO

OH

OH

OH

OHHO

O

(3S,4R,5R)-1,3,4,5,6-pentahydroxyhexan-2-one

HOOH

OHO

HO

O

OHOH

HO

HO O

OOH

OH

OHOH

OO

HO HOOH

HO

CHOOHHHHOOHHOHH

CH2OH(2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

(D) glucose

CHOOHHHHOOHHOHH

CH2OH

R

RR

S

(2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal(D) glucose

CHOOHHHHOOHHOHH

CH2OH

R

RR

S

CHOHHOHHOOHHOHH

CH2OH

RR

SS

(D) Mannose

CHOOHHHHOOHHOHH

CH2OH

R

RR

S

CHOHHOHHOOHHOHH

CH2OH

RR

SS

HNO3

CO2HOHHHHOOHHOHH

CO2H

RS

CO2HHHOHHOOHHOHH

CO2H

SS

SS

(2R,3S,4S,5S)-2,3,4,5-tetrahydroxyhexanedioic acid

SS

(2S,3S,4S,5S)-2,3,4,5-tetrahydroxyhexanedioic acid

CHOOHHOHHHHOOHH

CH2OH(2R,3R,4S,5R)-2,3,4,5,6-

pentahydroxyhexanal

Gulose

CHOHHOOHHHHOOHH

CH2OH

Iodose

(2S,3R,4S,5R)-2,3,4,5,6-pentahydroxyhexanal

CHOOHHHHOHHOOHH

CH2OH

Galactose

(2R,3S,4S,5R)-2,3,4,5,6-pentahydroxyhexanal

CHOHHOHHOHHOOHH

CH2OH(2S,3S,4S,5R)-2,3,4,5,6-

pentahydroxyhexanalTalose

CHOHHOOHHOHHOHH

CH2OH

Altrose

(2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

CHOOHHOHHOHHOHH

CH2OH(2R,3R,4R,5R)-2,3,4,5,6-

pentahydroxyhexanalAllose

Optically ActiveOptically Active Optically Active Optically Active Optically Active Optically Active

CO2HHHOOHHOHHOHH

CO2H

(2S,3R,4S,5S)-2,3,4,5-tetrahydroxyhexanedioic acid

CHOHHOOHHOHHOHH

CH2OH

Altrose

(2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

CHOOHHOHHOHHOHH

CH2OH(2R,3R,4R,5R)-2,3,4,5,6-

pentahydroxyhexanalAllose

Optically ActiveOptically Active

CO2HOHHOHHOHHOHH

CO2H(2R,3R,4S,5S)-2,3,4,5-

tetrahydroxyhexanedioic acid

Optically inactive

CO2HHO HHO HHO HHO H

CO2H(2R,3R,4S,5S)-2,3,4,5-tetrahydroxyhexanedioic acid

OHHOHHOHH

CH2OH

CHO

Ribose(2R,3R,4R)-2,3,4,5-tetrahydroxypentanal

1) NaCN, HCl 2) H2, BaSO43) aq. acid.

CHOHHOOHHOHHOHH

CH2OH

Altrose

(2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexanal

CHOOHHOHHOHHOHH

CH2OH(2R,3R,4R,5R)-2,3,4,5,6-

pentahydroxyhexa