Chapter 18, Problem 18.109EP

(a)

Interpretation Introduction

Interpretation: The name of the given compound has to be stated.

Concept introduction: In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.

Answer to Problem 18.109EP

The name of the given structure is methyl-$\alpha$-D-alloside.

Explanation of Solution

The Fisher projection formula for D-allose is,

The structure given in Problem 18-103 is,

The above structure is the cyclic form of monosaccharide D-allose.  Both the $-{\text{CH}}_{\text{2}}\text{OH}$ group and $-{\text{OCH}}_3$ group point in the opposite direction.  Therefore, the configuration is $\alpha$.  In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.  In the above structure, an $-{\text{OCH}}_3$ group is attached to the hemiacetal carbon.  Therefore, the name of the given structure is methyl-$\alpha$-D-alloside.

(b)

Interpretation Introduction

Interpretation: The name of the given compound has to be stated.

Concept introduction: In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.

Answer to Problem 18.109EP

The name of the given structure is ethyl-$\beta$-D-altroside.

Explanation of Solution

The Fisher projection formula for D-altrose is,

The structure given in Problem 18-103 is,

The above structure is the cyclic form of monosaccharide D- altrose. Both the $-{\text{CH}}_{\text{2}}\text{OH}$ group and $-{\text{OCH}}_2{\text{CH}}_{\text{3}}$ group point in the same direction.  Therefore, the configuration is $\beta$.  In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.  In the above structure, an $-{\text{OCH}}_2{\text{CH}}_{\text{3}}$ group is attached to the hemiacetal carbon.  Therefore, the name of the given structure is ethyl-$\beta$-D-altroside.

(c)

Interpretation Introduction

Interpretation: The name of the given compound has to be stated.

Concept introduction: In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.

Answer to Problem 18.109EP

The name of the given structure is ethyl-$\alpha$-D-fructoside.

Explanation of Solution

The Fisher projection formula for D-fructose is,

The structure given in Problem 18-103 is,

The above structure is the cyclic form of monosaccharide D-fructose. Both the $-{\text{CH}}_{\text{2}}\text{OH}$ group and $-{\text{OCH}}_2{\text{CH}}_{\text{3}}$ group point in the opposite direction.  Therefore, the configuration is $\alpha$.  In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.  In the above structure, an $-{\text{OCH}}_2{\text{CH}}_{\text{3}}$ group is attached to the hemiacetal carbon.  Therefore, the name of the given structure is ethyl-$\alpha$-D-fructoside.

(d)

Interpretation Introduction

Interpretation: The name of the given compound has to be stated.

Concept introduction: In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.

Answer to Problem 18.109EP

The name of the given structure is methyl-$\beta$-D-glucoside.

Explanation of Solution

The Fisher projection formula for D-glucose is,

The structure given in Problem 18-103 is,

The above structure is the cyclic form of monosaccharide D-glucose. Both the $-{\text{CH}}_{\text{2}}\text{OH}$ group and $-{\text{OCH}}_3$ group point in the same direction.  Therefore, the configuration is $\beta$.  In a cyclic monosaccharide, the replacement of an $-\text{OH}$ group of the hemiacetal carbon by an $-\text{OR}$ group results in the formation of an acetal.  The acetal formed is known as a glycoside.  The naming of Glycosides is done by first writing the alkyl substituent of $-\text{OR}$ group attached to the hemiacetal carbon, followed by the name of monosaccharide involved, with the suffix-ide appended to it.  In the above structure, an $-{\text{OCH}}_{\text{3}}$ group is attached to the hemiacetal carbon.  Therefore, the name of the given structure is methyl-$\beta$-D-glucoside.