Alkanolamine

In organic chemistry, alkanolamines (amino alcohols) are organic compounds that contain both hydroxyl (−OH) and amino (−NH₂, −NHR, and −NR₂) functional groups on an alkane backbone. Alkanolamine's bifunctionality and physicochemical characteristics lead to its use in many applications, such as textiles, cosmetics, agricultural chemical intermediates, drugs, and metal working fluids.^[1][2] Alkanolamines are present in many approved drugs and thousands of natural products.^[3] Two amino acids are alkanolamines, formally speaking: serine and hydroxyproline.

• Tropane alkaloids such as

• Alkanolamines
• 
  Methanolamine, from the reaction of ammonia with formaldehyde
• 
  Ethanolamine
• 
  2-Amino-2-methyl-1-propanol is a precursor to oxazolines
• 
  Valinol is derived from the amino acid valine
• 
  Sphingosine is a component of some cell membranes.

Alkanolamines usually have high-solubility in water due to the hydrogen bonding ability of both the hydroxyl group and the amino group.^[4] Alkanoamines have also shown a broad toxicity for a variety of organisms, including parasites, insect larvae and eggs, and microbes. Studies have also shown that the antimicrobial effect of alkanolamines increases in higher pH's.^[5] Most alkanolamines are colorless.^[6]

1-Aminoalcohols

1-Aminoalcohols are better known as hemiaminals. Methanolamine is the simplest member. 1-Aminoalcohols tend to be labile, readily converting to more highly condensed derivatives or hydrolyzing to the amine and carbonyl.

2-Aminoalcohols

Routes

2-Aminoalcohols are often generated by the reaction of amines with epoxides:

C₂H₄O + R−NH₂ → RNHC₂H₄OH

Hydrogenation or reduction of amino acids gives a large family of chiral 2-aminoalcohols:

RCH(NH₂)CO₂H + 2 H₂ → RCH(NH₂)CH₂OH + H₂O

Examples include prolinol (from proline), valinol (from valine), tyrosinol (from tyrosine). Some 2-aminoalcohols are produced by the Sharpless asymmetric amino hydroxylation.^[7]

Uses and examples

Simple alkanolamines are used as solvents, synthetic intermediates, and high-boiling bases.^[6]

2-Aminoalcohols have been used as synthetic building blocks and chiral auxiliaries.Amino ethanols have been proven to be vital precursors for chiral morpholines and piperazines.^[3][8] Key members: ethanolamine, dimethylethanolamine, N-methylethanolamine, Aminomethyl propanol. Two popular drugs, often called alkanolamine beta blockers, are members of this structural class: propranolol, pindolol.^[9][10][11] 2-Aminoalcohols can also be found in the direct action subgroup of adrenergic drugs such as epinephrine, isoproterenol, phenylephrine and isoetarine.^[12]

Other medicinally useful derivative of ethanolamine: Isoetarine, veratridine, veratrine, epinephrine (adrenaline), norepinephrine (noradrenaline), atropine.

1,3- to 1,7-amino alcohols

Two examples of longer aminoalcohols include Heptaminol, a cardiac stimulant, and propanolamines.

1,3-Aminoalcohols are present in several bioactive molecules, such as Sedinone, Dumetorine, and Hygroline.^[13] 1,3-Aminoalcohols have be synthesize through a couple methods. Similar to 2-aminoalcohols, 1,3 aminoalcohols can be formed through ring openings, such as an azo-ring opening and addition.^[13] 1,3-aminoalcohols can also be synthesized through an azo-aldol condensation or an intermolecular C-H activation.^[13]

1,4 and 1,5-aminoalcohols have been synthesized through the reduction of cyclic amides.^[14] Catalyzed alkylation of primary amines with 1,4-butanediol is another synthetic route for 1,4-aminoalcohols.^[14] Larger amino alcohol (1,5 - and up) synthesis is comparatively underdeveloped. Electrochemical ring-openings can produce 1,3 to 1,7-aminoalcohols.^[15]