Fundamentals of Medicinal Chemistry

1.5.3 Acylglycerols (glycerides)

Acylglycerols are the mono-, di- and tri-esters of glycerol and fatty acids (Figure

1.22). The fatty acid residues of di- and tri-esters may or may not be the same.

Tri-esters are the most common naturally occuring acylglycerols.

Complex mixtures of acylglycerols are the major components of naturally

occuring fats and oils. Oils are fats that are liquid at room temperature. Their

liquidity is attributed to their acid residues having a high proportion of C¼C

bonds. Triacylglycerols are the predominant energy store in animals and are

mainly located in adipose tissue.

Metabolism of fats is responsible for supplying a significant part of the energy

requirements of many cells. Initially the fat is hydrolysed to glycerol and the

appropriate fatty acids. Metabolic oxidation of these fatty acids liberates energy

in a form that can be utilized by the cell.

Key:

R^1 = Palmitic acid,

R^2 = Stearic acid,

R^3 = Oleic acid.

OH

OH

CH 2

CH

CH 2

OH

2

11

2

3 3

1-Palmitoylglycerol

Glyceryl 1-palmitate

OH

OH

CH 2

CH

CH 2

OCOR^1

OCOR^2

OH

CH 2

CH

CH 2

OCOR^2

2-Palmitoylglycerol

Glyceryl 2-palmitate

1,2-Distearoylglycerol

Glyceryl 1,2-distearate

OH

OH

CH 2

CH

CH 2

OCOR^1

OH

OCOR^2

CH 2

CH

CH 2

OCOR^1

OCOR^3

OCOR^2

CH 2

CH

CH 2

OCOR^3

OCOR^2

OCOR^2

CH 2

CH

CH 2

OCOR^2

1-Palmitoyl-3-stearoylglycerol

Glyceryl 1-Palmito-3-stearate

Glycerol

1,2-Oleoyl-3-stearoylglycerol

Glyceryl dioleostearate

Tristearoylglycerol

Glyceryl tristearin

Figure 1.22 Examples of the nomenclature and structures of acylglycerols. Several systems, includ-

ing the IUPAC system for esters, are used to name acylglycerols. In addition to the IUPAC system,

two nomenclature systems are in common use. The first uses glycerol as a stem name, the fatty acid

residuesbeingindicatedbytheiracylprefixestogetherwithanappropriatelocant.Thesecondsystem

uses glyceryl followed by the names of the acid residues arranged in the order they appear in the

molecule. However, the ending-icof the acid is replaced by the suffix-oexcept for the last residue,

which is given the ending-ate. The suffix-inis used when all three fatty acid residues are identical

1.5.4 Steroids

Steroids are compounds based on fused multi-ring carbon skeletons, each ring

being referred to by a letter (Figure 1.23(a)). The rings may be saturated or

LIPIDS 21