Maillard-type condensation

A Maillard-type condensation reaction is likely to occur between lactose and compounds with a primary amine group to form brown, or yellow-brown-colored products. ... 

The Brimble group reported the synthesis of acortatarin A 20 in 2012. As in the first synthesis of acortatarin A 20 by Sudhakar et al. a traditional acid-catalyzed dehydrative spiroketalization was used as one of the final steps. However, instead of performing the previously used disconnection between CIO and N9, as several other groups have reporteda Maillard-type condensation reaction between amino alcohol 50 and the sugar surrogate 51 would be used to give 49. The amine 50 would come from D-mannitol and 51 would be prepared from furfuryl alcohol on a gram scale (Scheme l )" ... 

The use of a Maillard-type condensation to form the pyrrole fragment for the spiroketalization is rather interesting since the biosynthesis proposed by Peterson and co-workers (Scheme 10) suggests that Nature uses a similar reaction to form acortatarin A 20. In the end, they were able to access acortatarin A 20 in 14 steps, if again one does not count the steps necessary to convert D-mannitol into the cyclohexylidene glyceraldehyde 52. 

The polymeric material from the plain caramel is generated from the condensation reactions of the aldehydes and ketones formed by heating the sugar with bases or acids. The ammonia caramel is formed in a Maillard type reaction [2] where carbonyl compounds react with amino groups or ammonia. This type of compound will be further presented in Sections 11.2 and 11.3. Sulfite caramel is also a Maillard type polymer. However, as hydrogen sulfites form stable adducts with aldehydes and ketones, the sulfite caramels include in their structure sulfite groups. 

Since the pioneering synthesis of this type of glycoconjugate first described by Maillard el al. in the late 1980s via condensation of 2-formylphenyl tetra-O-acetvl-/)-D-glucopyranoside with pyrrole,132 improved synthetic methodologies have generated... 

Another major problem associated with the extraction of DNA from archaeological specimens is that the procedure often co-extracts impurities that can later complicate, or prevent, the study of the extracted DNA by inhibiting PCR amplification (reviewed by 5). Commonly encountered inhibitory substances found in aDNA extracted from teeth, bones, mummified tissue, and coprolites include humic acids, ftilvic acids, tannins, porphyrin products, phenolic compounds, hematin, and collagen type I (37—42). The formation of Maillard products, commonly encountered in coprolite samples, can also prevent PCR amplification by causing DNA to become inaccessibly trapped in these sugar-derived condensation products (12). As the negative results in many aDNA studies are attributed to the presence of PCR inhibitors, our extraction method outlined below pays particular attention to the problem and offers a simple test for the presence of PCR inhibitors in DNA extracts. 

Apart from sotolon, the other compounds in Fig. 5 can be explained as the products of a Maillard reaction, and their carbon skeletons simply originate from the active Amadori intermediate in other words, they still preserve the straight carbon chain structure of monosaccharides. In spite of being a simple Cg lactone, sotolon has a branched carbon skeleton, which implies another formation process in the Maillard reaction. Sulser e al.(6) reported that ethyl sotolon (ll) was prepared from threonine with sulfuric acid, and that 2-oxobutyric acid, a degradation product of threonine, was a better starting material to obtain II. This final reaction is a Claisen type of condensation, which would proceed more smoothly under alkaline conditions. As we(lO) obtained II from 2-oxobutyric acid (see figure 6) with a high yield in the presence of potassium carbonate in ethanol, a mixed condensation of 2-oxobutyric and 2-oxo-propanoic (pyruvic) acids was attempted under the same conditions, and a mixture of sotolon (22% yield) and II were obtained however, the... 

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