Concise and Straightforward Asymmetric Synthesis of a Cyclic Natural Hydroxy-Amino Acid

Abstract

An enantioselective total synthesis of the natural amino acid (2S,4R,5R)-4,5-dihydroxy-pipecolic acid starting from D-glucoheptono-1, 4-lactone is presented. The best sequence employed as a key step the intramolecular nucleophilic displacement by an amino function of a 6-O-p-toluene-sulphonyl derivative of a methyl D-arabino-hexonate and involved only 12 steps with an overall yield of 19%. The structures of the compounds synthesized were elucidated on the basis of comprehensive spectroscopic (NMR and MS) and computational analysis.

Phenolic Compounds in Chilean Mistletoe (Quintral, Tristerix tetrandus) Analyzed by UHPLC–Q/Orbitrap/MS/MS and Its Antioxidant Properties

“…Indeed, LC-MS was used for the analysis of carotenoids [20], anthocyanins [21], phenolic acids [22] and alkaloids [23] in edible fruits and flowers, among other constituents. Since we were not able to find LC-MS analyses nor reports on phytochemical compounds from this mistletoe species or related ones, and in continuation of our search for interesting polyphenols and other bioactive compounds in native Chilean plants [24,25,26,27,28], in the present work the polyphenolic fingerprints and phenolic content of the leaves and flowers of this species (Figure 1) from the VIII region of Chile were correlated with the antioxidant capacities measured by the bleaching of the DPPH radical, the ferric reducing antioxidant power (FRAP), the superoxide anion scavenging activity assays (SA). The compounds were identified for the first time with the help of PDA analysis and high resolution Orbitrap mass spectrometry (HPLC-ESI-OT-MS) plus comparison with authentic standards.…”