Carboxylic acids unsaturated analogues

Oxetanes can be formed by intramolecular reaction between a carbonyl group and an alkene, and this has been used (4.74) in making analogues of thromboxane A, (one of the compounds responsible for the control of blood clotting), albeit usually as the minor product. A special case of intramolecular reaction is seen for a,p-unsaturated carboxylic acids 14.75), where the product is an oxete that is tautomeric with a p-lactone. Oxetes may also be formed by photocycloaddition of ketones or aldehydes with alkynes the oxete normally ring-opens at room temperature to give an a,p-unsaturated carbonyl compound (4.76), but at lower temperatures its spectral... 

This type of disconnection is mainly used for the preparation of dipeptides of type Xaai >[ , CH=CH]Gly. It allows control of the stereochemistry of the Xaa residue by starting from chiral a-amino aldehydes. For the construction of the /ram -p,y-unsaturated carboxylic acid moiety, the use of the triphenylphosphonium salt 31 (Scheme 9) derived from 3-chloro-propanoic acid was not suitable.14 Instead, the trimethylsilylprop-2-ynyl phosphonium salt 33 serves as a three-carbon unit, which can be converted into the P,y-unsaturated acid by hydroboration and oxidation. The required Boc-protected a-amino aldehyde 32 can be prepared using virtually racemization-free procedures. 37 However, at the end of the reaction sequence, racemization has been detected, especially for Boc-Phet )[ , CH=CH]Gly-OH, but not for the Ala and Pro analogues. 63 A mixture of E- and Z-enynes 34 and 35 is formed (8 2 to 9 1), which can be separated by column chromatography. 4,48 50 53 64 65 ... 

The application of 4-oxo-4-arylbut-2-enonic acids 274 as unsaturated carbonyls in reactions with anilines allows the synthesis of quinoline-2-carboxylic acids 275 [212] (Scheme 3.76). Reactions of anilines with arylidenepyruvic acids can also yield quiniline carboxylic acids (or their decarboxylated analogues)... 

In the pioneering work by Wilcox and Gaudino, a straightforward route to the carbocyclic analogue of D-fructofuranose, 64, and its 6-phosphate derivative was delineated [14a,b]. As shown in Scheme 9, the first move consisted of Wittig olefination of benzyl-protected arabinose 60 with carboxy-tert-butylmethylene triphenyl phosphorane to deliver unsaturated ester 61, which was then cleverly elaborated into dibromide 62 via a reaction cascade encompassing Swem oxidation of the secondary OH, ester hydrolysis, diastereoselective addition of dibromomethyl lithium, and carboxylic acid methylation. 

Alicyclic P-lactams 28 were successfully synthesized via a parallel liquid-phase Ugi four-center three-component reaction, starting from alicyclic P-amino acids such as cis-2-aminocyclohexanecarboxylic acid, c/.s-2-aminocyclopentanecarboxylic acid, 2,3-diexo-3-aminobicyclo-[2.2.1]heptane-2-carboxylic acid and some of their partially unsaturated analogues <02OL1967>. 

Reactions of Phosphoric Acid Derivatives.— Interest in HMPT both as a solvent and as a reactant continues. In this solvent / -unsaturated carboxylic acids are reduced by lithium to mixtures of the saturated analogues and synunetrically substituted adipic acids addition of lithium acetate gives reasonable yields of substituted glutaric acids, probably by initial metallation by lithium diethylamide (Scheme 2). Butyl-lithium, however, cleaves... 

In the selection of an appropriate corrosion inhibitor, an important consideration is the problem of adverse competition with other additives designed to adsorb on the liquid-metal interface. Extreme pressure and/or antiwear agents compete for the same sites as the corrosion inhibitor. Eatty amines are good corrosion inhibitors in this type of environment. However, their adverse effect on the performance of ZDDP additives often prohibits their use. Half esters or amides of dodecylsuccinic acid, phosphate esters or thiophosphates are frequently employed. A combination of inhibitors is sometimes used, for example, fatty carboxylic acids or the dimer/trimer analogues of the unsaturated acids, e.g. oleic, used in conjunction with an amine such as an ethanolamine or alkyl amine, or amide such as alkyl imidazoline and sarcosines, Eig. 6.7. Shorter chain carboxylic acid and amines are used as volatile corrosion inhibitors. 

Due to the natural occurrence and the novel biological activity, interest in investigations of alicyclic P-amino acids has been aroused. A number of new enantioselective syntheses have been developed and protected by patents [14-26]. The writing of this review was prompted by the renewed interest in the title compound 1. The primary focus was its synthesis and some of its transformations. Besides 1, other alicyclic p-amino acids, such as cis- and trans-2-aminocyclohexanecarboxylic acid (2), 2,3-diendo- and 2,3-c exo-3-aminobicyclo[2.2.1]heptane-2-carboxylic acid (3) and some of their partially unsaturated analogues and derivatives will be mentioned. The biological properties of these and related compounds will also be discussed. 

Ammonolysis of alicyclic anhydrides followed by Hofmann degradation is one of the most frequently used methods for the synthesis of alicyclic P-amino acids, since many anhydrides are commercially available cheap substances produced by Diels-Alder addition of maleic anhydride and the corresponding dienes [44], By this method, cis- and frans,-2-aminocyclohexane- and -cyclohexenecarboxylic acids, cis-2-aminocycloheptanecarboxylic acid [45], 3-ewtffo-aminobicyclo [2.2.1 ]heptane-2-ew/o-carboxylic acid, 3-e ifo-aminobicyclo[2.2.1 ]hept-5-ene-2-ertcarboxylic acid and some analogue P-amino acids have been prepared [44, 46-48], For partially unsaturated alicyclic compounds, a modified Hofmann degradation is used, sodium hypochlorite being applied to avoid bromine addition to the double bond [48,49]. 

Lactams - Cyclic amides of amino carboxylic acids, having a 1-azacycloalkan-2-one structure, or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. [5]... 

---