Hydroxycarboxylic acid derivs

Boron enolates containing the chiral information in C2-symmetric ligands of the metal atom, also provide rmt/-/ -hydroxycarboxylic acid derivatives of high optical purity34 -64-70. When 5-(3-cthylpent-3-yl) thiopropanoate is treated with (5,5)-2,5-dimethyl-l-(trifluoromethylsul-... 

Oxazol-4-ones 132 have been prepared by Trost and co-workers via a microwave-assisted cyclocondensation of bromo imides in the presence of NaF [86]. These products where then employed for a Mo-catalyzed asymmetric synthesis of Q -hydroxycarboxylic acid derivatives 134 (Scheme 47). 

Dochnahl M, Fu GC (2009) Catalytic asymmetric cycloaddition of ketenes and nitroso compounds enantioselective synthesis of a-hydroxycarboxylic acid derivatives. Angew Chem Int Ed 48 2391-2393... 

Mur 207), has received renewed interest in recent years. A fine review covering the intermolecular asymmetric Diels-Alder reaction was compiled by Mori 208>. In this article the use of terpenes and carbohydrates as chiral auxiliaries is discussed no amino acid derivatives are mentioned in this context. A chiral a-hydroxycarboxylic acid derivative was also used to achieve an asymmetric Diels-Alder reaction 209). High asymmetric induction could be detected in the intramolecular Diels-Alder reaction of chiral molecules. 

In the polycondensation of aliphatic dicarboxylic acids with diols, DCC is used to mediate the reaction. In this manner biodegradable and surface active aliphatic polyesters are obtained. Also, hydroxycarboxylic acids derived from maleic or succinic acid are ho-mopolymerized in the presence of EDCCl in DMF at room temperature. In this manner... 

The regioselective process is suitable for the synthesis of protected (3-amino-a-hydroxycarboxylic acid derivatives (racemic, no chiral ligand added) from the corresponding acrylic acid substrates. On the other hand, 1,4-bis(dihydroquininoxy)-anthraquinone mediates enantioselective formation of A-benzyloxycarbonylphenylserine. ... 

The alternative procedure for chiral 4-substituted-2-oxetanones is the ring closure of optically active 3-hydroxycarboxylic acid derivatives [49]. 

O-SuIfonyl-a-hydroxycarboxylic acids a-Hydroxycarboxylic acid derivatives... 

Optically active 3-amino-2-hydroxycarboxylic acid derivatives are often key components of medicinally important compounds. The synthesis of isopropyl (2i ,35)-3-amino-4-cyclo-hexyl-2-hydroxybutyrate (126) (Scheme 28) takes advantage of a [2 + 2]-cycloaddition reaction of the chiral imines 123, prepared from 63, to assemble the important diastereomeric azetidinone 124 as the crucial precursor for completion of this novel synthesis. Protection of the hydroxy group of 63 as either the TBS ether 119 or the tert-buty ether 120, followed by a DIBAL reduction at —78 °C, produces smoothly one of the aldehydes 121 or 122. Condensation of these aldehydes with either di-p-anisylmethylamine or benzylamine in the presence of anhydrous magnesium sulfate affords the four possible chiral imines 123a—d (Scheme 26). 

Similar polyacetal structures were prepared by BASF scientists from general dialdehydes and aliphatic hydroxycarboxylic acids derived from sugars [156, 157], shown in Scheme 15. Alternatively, carboxypolyacetals are available by the addition of polyhydroxy carboxylic acids, tartaric acid, for example, to divinyl ethers [158]. 

This stoichiometric chemistry has been revisited in the last few years [60,79-82] and, for instance, applied to the s)mthesis of a-methylene-y-hydroxy carboxylic acids and their derivatives (c/s-p.y-disubstituted a-methylene-y-lactones) by means of nickel-mediated sequential addition of carbon dioxide and aldehydes into terminal or internal allenes [80, 81], or exploited for the preparation of P-hydroxycarboxylic acid derivatives by 02-oxidation of the Ni-n -allyl species (5.8)... 

Lactones occur as natural odorants in aU major food commodities, including meat and meat products, milk, dairy products, cereals, fruits, vegetables and various beverages, such as tea, wine and spirits. Odour-active compounds in foods are y-and 5-lactones derived from aliphatic saturated and unsaturated y-hydroxycarboxyHc and 5-hydroxycarboxylic acids derived from fatty acids or sugars, but some lactones also arise from other precursors (e.g. mint lactone is a terpenoid compound and pantolactone is produced by hydrolysis of pantothenic acid via pantoic acid). Some lactones derived from aromatic hydroxycarboxyhc acids are also common compounds. The most important representatives of these compounds are phthahdes that are 3fL-isobenzofuran-l-ones (8-98) and coumarins (8-99) that are 2fL-l-benzopyran-2-ones (5-lactones of 2-hydroxycinnamic acids). 

Billich, A., Charpiot, B., Ettmayer, R, Gstach, H., Lehr, R, and Scholz, D. Rreparation of 2,4-diamino-3-hydroxycarboxylic acid-derivative HIV proteinase inhibitors. ER615969, 1994, Sandoz Ltd., Switzerland Sandoz-Ratent-G.m.b.H. Sandoz-Erfindungen Verwaltungsgesellschaft m.b.H. 

Figure 11.77 Enantioselective reduction of an aryl f CIalkyl ketone using stoichiometric amounts of (+ )-lpc2BCI synthesis of an e.p. substituted y-hydroxycarboxylic acid derivative...

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