Lactic acids, substituted

Chemical Properties. Its two functional groups permit a wide variety of chemical reactions for lactic acid. The primary classes of these reactions are oxidation, reduction, condensation, and substitution at the alcohol group. 

Substitution at the Alcohol Group. Acylation of the OH group by acylating agents such as acid chlorides or anhydrides is one of the important high yielding substitution reactions at the OH group of lactic acid and its functional derivatives. AUphatic, aromatic, and other substituted derivatives can be produced. 

The acidic sugars discussed in this Section are glycuronic acids and glycu-losonic acids. Bacterial polysaccharides may also become acidic by substitution of sugar residues, for example by etherification with lactic acid, acetala-tion with pyruvic acid, or phosphorylation, and these possibilities will be discussed in the following Sections. A sugar that does not fall into any of... 

A more recent synthesis of 197 [365] is shown in Fig. 9. Enders introduced the stereogenic centre of (S)-lactic acid into the crucial position 10 in 197. The vinylsulfone B, readily available from lactic acid, was transformed into the planar chiral phenylsulfonyl-substituted (q3-allyl)tetracarbonyliron(+l) tetra-fluoroborate C showing (IR,2S,3 )-configuration. Addition of allyltrimethyl silane yielded the vinyl sulfone D which was hydrogenated to E. Alkylation with the dioxolane-derivative of l-bromoheptan-6-one (readily available from 6-bro-mohexanoic acid) afforded F. Finally, reductive removal of the sulfonyl group and deprotection of the carbonyl group furnished 197. A similar approach was used for the synthesis of 198 [366]. 

The pyridine subcycle unit has been introduced into a wide range of 18-crown-6 derivatives. For example, reaction of 2,6-pyridinedicarbonyl chloride with the dimethyl substituted tetraethylene glycol (SS)-84, derived from (S)-lactic acid, afforded (126) the chiral macrocyclic polyether diester (5S)-184. A similar preparative approach (127) gave (SS)-185, where the source of the chirality is (5)-mandelic acid. 

The names propanoic acid (systematic) and propionic acid (retained) are both approved for the unsubstituted acid. However, the acid CI-CH2-CH2-COOH must be named systematically as 3-chloropropanoic acid. The acid CH3-CH(OH)-COOH is known as lactic acid, if unsubstituted when it is substituted in position 3, for example with chlorine, the name becomes 3-chloro-2-hydroxypropanoic acid. Names such as 3-chloro-2-hydroxypropionic acid or 3-chlorolactic acid are not acceptable. 

Klok H-A, Hwang JJ, Hartgerink JD, Stupp SI. Self-assemhling biomaterials L-lysine-dendron-substituted cholesteryl-(L-lactic acid). Macromolecules 2002 35 6101-6111. 

The enolates of l,3-dioxolan-4-ones 1 and l,3-oxathiolan-4-ones2, which are y-lactones substituted with a heteroatom, can be prepared using normal conditions (LDA, THF) and subsequently alkylated. If one takes, e.g.. a nonracemic a-hydroxy acid such as lactic acid 3, then on formation of the heterocycles 1 (R1 = CH3 R2 = alkyl) chirality is transferred from the a-po-sition (C-5) in the starting acid to C-2 in 1, forming (2R,5R)-4 and (2S,5R)-5. If 4 and 5 are easily separable or, even better, if one of them is formed diastereoselectively from 3 then 4 and/or 5 can be transformed to the respective enolates 6 and 7 and alkylated with R X. 

Komoto detected lactic acid in the mixture from reaction of D-glucose with ammonia,4 and presumed that it was produced from pyruvaldehyde formed by decomposition of D-glucose. Lactic acid has, indeed, been found as a product of the action of alkali (lime-water) on substituted D-glucose and substituted D-fructose,81,83,96 and the mechanism of its formation involves the reversible aldol reaction, followed by formation of pyruvaldehyde, and the benzilic acid rearrangement already described for saccharinic acid this is illustrated83,96 in Scheme 11. 

A comparison of these formula) with those of lactic and para lactic acids (p. 827) shows at a glance that No. 1 is the chloropropionie acid which yields lactic acid, whilst No. 2 is iso cbloropropiouic acid, which, by the substitution of its chlorine by hydroxyl, must yield pathetic acid. By the action of nascent hydrogen, both isomeric chlorides will obviously produce the same propionic acid. 

Chirality (handedness, from Greek cheir = hand) is the term used for objects, including molecules, which are not superposable with their mirror images. Molecules which display chirality, such as (S)-(+)-lactic acid (/, Fig. 1) are called chiral. Chirality is often associated with a chiral center (formerly called an asymmetric atom ), such as the starred carbon atom in lactic acid (Fig. 1) but there are other elements that give rise to chirality the chiral axis as in allenes (see below) or the chiral plane, as in certain substituted paracyclophanes.1,2)... 

Several gitonic superelectrophiles have been reported having closely oriented oxonium and carboxonium ion centers, some of which may be considered 1,3-dications. A series of hydroxy-substituted carboxylic acids were studied in FSOsH-SbFs in solution and the oxonium-carbonium dications could be directly observed at low temperature.57 In the case of lactic acid, dication 147 is a persistent ion at — 80°C, but at temperatures above — 60°C, formation of the diprotonated lactide (148) is observed (eq 48). 

P Jeschke, G Bonse, G Thielking, W Etzel, A Harder, N Mencke, H Kleinkauf, R Zocher, K Iinuma, K Miyamoto. Process for the preparation of substituted aryl lactic acid containing cyclodepsipeptides with 24 ring atoms. WO9720945 (Bayer AG), 1998. 

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