A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses: the two enantiomers of glyceraldehyde, which are aldoses; and dihydroxyacetone, a ketose which is symmetrical and therefore has no enantiomers.

Aldohexoses: 6 carbon sugars with four chiral centers. Aldohexoses have sixteen (2 4) possible stereoisomers. five pairs of D/L enantiomers called allose, altrose, glucose, mannose, gulose, idose, galactose, and talose.

Stereochemistry of Monosaccharides The simplest sugars are the trioses. The possible trioses are shown in part (a) of Figure 6.3.2 6.3. 2; glyceraldehyde is an aldotriose, while dihydroxyacetone is a ketotriose. Notice that two structures are shown for glyceraldehyde.

Aldotriose: Dihydroxy aldehydes having three carbon atoms are referred to as aldotriose. Since there is only one asymmetric carbon (n = 1), only two (2 1 = 2) optically active forms of aldotriose exist, i.e., d -glyceraldehyde and l -glyceraldehyde (Fig. 2.3), which are mirror images (enantiomer) of each other.

Classify monosaccharides as aldoses or ketoses and as trioses, tetroses, pentoses, or hexoses. Distinguish between a D sugar and an L sugar. The naturally occurring monosaccharides contain three to seven carbon atoms per molecule.

An aldotriose is a specific type of monosaccharide, which is a simple sugar consisting of a single sugar unit. More specifically, an aldotriose is a triose sugar that contains an aldehyde functional group (-CHO) as its most oxidized or terminal functional group.

An aldotetrose is a four-carbon sugar with two chirality centers. Thus, there are 2 2 = 4 possible stereoisomeric aldotetroses, or two D, L pairs of enantiomers named erythrose and threose. Aldopentoses have three chirality centers and a total of 2 3 = 8 possible stereoisomers, or four D, L pairs of enantiomers.

A three-carbon sugar is called a triose (an aldotriose or ketotriose). From: Guide to Biochemistry, 1989

Glyceraldehyde, an aldotriose and the simplest naturally occurring carbohydrate, has the structure shown below. Because four different groups are bonded to the number 2 carbon atom, this molecule is also chiral.

Four of the possible aldopentoses are D sugars, while the other four have an L configuration: Among these, D-Ribose is the most common and perhaps important as it is the sugar building block of the DNA backbone in the deoxy form (Deoxyribo nucleic acid).