70363-24-5Relevant articles and documents
HR-MALDI-MS imaging assisted screening of β-Carboline alkaloids discovered from mycena metata
Jaeger, Robert J. R.,Lamshoeft, Marc,Gottfried, Sebastian,Spiteller, Michael,Spiteller, Peter
, p. 127 - 134 (2013/06/27)
Fruiting bodies of Mycena metata were screened for the presence of new secondary metabolites by means of HPLC-UV, LC-HR-ESIMS, and high-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (HRMALDI- MS imaging). Thus, a new β-carboline alkaloid, 6-hydroxymetatacarboline D (1d), was isolated from fruiting bodies of M. metata. 6-Hydroxymetatacarboline D consists of a highly substituted β-carboline skeleton, which is likely to be derived biosynthetically from L-tryptophan, 2-oxoglutaric acid, L-threonine, and L-proline. The structure of the alkaloid was established by 2D NMR spectroscopic methods and HR-ESIMS. Moreover, by extensive application of LC-HR-ESIMS, LC-HR-ESIMS/MS, and LC-HR-ESIMS3 techniques we were able to elucidate the structures of a number of accompanying β-carboline alkaloids, 1a- 1c, 1e-1i, and 2a-2g, structurally closely related to 6-hydroxymetatacarboline D, which are present in M. metata in minor amounts. The absolute configuration of the stereogenic centers of the β-carboline alkaloids was determined by GC-MS comparison with authentic synthetic samples after hydrolytic cleavage and derivatization of the resulting amino acids.
Asymmetric synthesis of α-amino acids based on carbon radical addition to glyoxylic oxime ether
Miyabe, Hideto,Ushiro, Chikage,Ueda, Masafumi,Yamakawa, Kumiko,Naito, Takeaki
, p. 176 - 185 (2007/10/03)
The first asymmetric synthesis of α-amino acids based on diastereoselective carbon radical addition to glyoxylic imine derivatives is reported. The addition of an isopropyl radical, generated from i-PrI, Bu3SnH, and Et3B in CH2Cl2 at 25 °C, to achiral glyoxylic oxime ether 1 proceeded regioselectively at the imino carbon atom of the oxime ether group to give an excellent yield of the C-isopropylated product 2. The competitive reaction using glyoxylic oxime ether 1 and aldoxime ether 4 showed that the reactivity of the glyoxylic oxime ether toward nucleophilic carbon radicals was enhanced by the presence of a neighboring electron-withdrawing substituent. Thus, the alkyl radical addition to glyoxylic oxime ether 1 proceeded smoothly even at -78 °C, in contrast to the unactivated aldoxime ether 4. A high degree of stereocontrol in the carbon radical addition to the glyoxylic oxime ether was achieved by using Oppolzer's camphorsultam as a chiral auxiliary. The stannyl radical-mediated reaction of the camphorsultam derivative 6 with an isopropyl radical at -78 °C afforded a 96:4 diastereomeric mixture, 7a, of the C-isopropylated product. The reductive removal of the benzyloxy group of the major diastereomer (R)-7a, by treatment with Mo(CO)6 and the subsequent removal of the sultam auxiliary by standard hydrolysis, afforded the enantiomerically pure D-valine (R)-12 without any loss of stereochemical purity. To evaluate the new methodology, a variety of alkyl radicals were employed in the addition reaction which gave the alkylated products 7 with excellent diastereoselectivity, allowing access to a wide range of enantiomerically pure natural and unnatural α-amino acids. Even in the absence of Bu3SnH, treatment of 6 with alkyl iodide and Et3B at 20 °C gave the C-alkylated products 7 with moderate diastereoselectivities. The use of Et2Zn as a radical initiator, instead of Et3B, was also effective for the radical reaction. The enantioselective isopropyl radical addition to 1 using (R)-(+)-2,2'-isopropylidenebis(4-phenyl-2-oxazoline) and MgBr2 gave excellent chemical yield of the valine derivative 2 in 52% ee.
Expeditious synthesis of Mosher amides using a solid supported carbodiimide
Adamczyk, Maciej,Fishpaugh, Jeffrey R.
, p. 7171 - 7172 (2007/10/03)
A novel method of Mosher amide synthesis using a solid supported carbodiimide in CDCl3 is described. Estimation of optical purity can be promptly achieved by direct NMR analysis of the reaction solvent.
Elucidation of the absolute configurations of amino acids and amines by the modified mosher's method
Kusumi, Takenori,Fukushima, Toshiro,Ohtani, Ikuko,Kakisawa, Hiroshi
, p. 2939 - 2942 (2007/10/02)
Application of the modified Mosher's method to the N-MTPA derivatives of several amino acid esters and acyclic amines indicates that this method may be generally used to determine the absolute configurations of the α-carbons of amino compounds of less tha
