B. Wegrzynski

aS,7S-absolute configuration of natural (−)-colchicine and allocongeners

The aS,7S‐absolute configuration of (−)‐colchicine (1) and (−)‐N‐acetylcolchinol methyl ether (3, NCME) suggested on the basis of 1H NMR data and negative Cotton effects at about 260 nm (EtOH) is firmly established by an X‐ray analysis of urea 5, a compound derived from 3. Binding of these compounds to tubulin requires an aS‐configuration of the biaryl system.

Chiroptical properties of fluorescamine condensation compounds with α-amino acids in situ

Summary Fluorescamine reacts efficiently with primary amino acids to form pyrrolinone-type chromophores. A simple test tube procedure is described which allows in situ determination of absolute configuration of α-amino acids based on the chiroptical properties of these chromophoric derivatives.

Precursors of the mammalian synthesis of morphine: (+)‐salutaridine and (−)‐thebaine from (+)‐6‐demethylsalutaridine, and (−)‐N‐13CH3‐thebaine from (−)‐northebaine

Standard samples of pure (+)‐salutaridine and (−)‐thebaine required to study the mammalian origin of morphine, were prepared from (+)‐6‐demethylsalutaridine by published procedures and were characterized by CD spectra and physical data. Reductive N‐methylation of (−)‐northebaine afforded (−)‐thebaine, and when 13C‐labeled formalin was used, (−)‐thebaine with a 13C label on the N‐methyl carbon atom resulted. The latter represents a model procedure to prepare ultimately N‐14CH3‐labeled (−)‐thebaine and 14C‐labeled congeners.

Chiroptical properties of fluorescamine condensation compounds with secondary amino acids insitu

Abstract Secondary amino acids react readily with fluorescamine to form aminoenone-type chromophores with long wavelength absorption maxima at 300–320 nm. The chiroptical properties of the reaction mixtures allow one to determine the absolute configuration of secondary amino acids in situ .

A Fast and Simple in Situ Method for the Determination of the Absolute Configuration of 2-and 3-Hydroxycarboxylic Acids, Esters and Ethers Using the Chiroptical Properties of Their Eu(Fod)3 Complexes. A Preliminary Report

Abstract The NMR shift reagent Europium (III)-tris-(1,1,1,2,2,3,3)-heptafluoro-7,7-dimethyl-4,6-octanedione [Eu(fod)3) complexes efficiently with chiral 2- and 3-hydroxycarboxylic acids, esters and ethers in chloroform. These complexes exhibit characteristic circular dichroism (CD) spectral pattern in the 350–250 nm region. A fast and simple procedure (also in micro scale) has been worked out which utilizes the signs of these CD bands for the determination of the absolute configuration at the C-2 or C-3 carbon in situ. In D(R)-series1, a negative CD band is observed at around 310 nm and a positive one in the 290 nm region. The CD spectra of the Eu complexes of L(S)-enantiomers are mirror images of those of D(R)-ones. An empirical rule has been proposed.

Application of fluorescamine XII. Chiroptical properties of fluorescamine condensation compounds with some less common α-amino acids

Abstract Fluorescamine (FLURAM®) reacts efficiently with less common chiral α-amino acids to form pyrrolinone-type chromophores. The characteristic Cotton effects at 324-300 and at 290-263 nm can be related to the absolute configuration of the parent α-amino acid without isolation of the products. These CD bands are negative and positive, respectively, for the derivatives of the L-α-amino acids.

Chiroptical properties of fluorescamine condensation compounds with amino acid esters in situ. Pyrrolinone chirality rule

Abstract Chiral α-amino acid esters react readily with fluorescamine (Fluram®) to form pyrrolinone-type chromophores. The characteristic Cotton effects given by these chromophoric derivatives provide a means for the determination of the absolute configuration of the parent amino acid ester. The strong CD band in the 330-320 nm region of the L-amino acid ester derivative is always negative, while it is positive for the D-amino acid ester derivatives. A pyrrolinone chirality rule is proposed to explain the sign of this Cotton effect.

Chiroptical properties of fluorescamine condensation compounds with dipeptides in situ

Abstract The free amino group of a dipeptide reacts efficiently with fluores-camine (FLURAM ® ) to form pyrrolinone-type chromophores with long wavelength absorption maxima in the 380 nm region. A simple test tube procedure is described which allows in situ determination of the absolute configuration of the NH 2 -terminal amino acids of the dipeptides based on the chiroptical properties of their chromophoric derivatives.

Application Of Fluorescamine Xiv1. Determination Of Optical Purity Of A Small Amount Of Amino Acids By The Fluorescamine Method

Abstract A new simple and fast micro method has been established to determine the optical purity of a small amount of amino acids (0.1–1 μg/ml). The amino acids react readily with fluorescamine to form pyrrolinone-type chromophores, which show strong CD bands at 400–300 nm and much larger optical rotation than the free amino acids in the visible spectral range.

Application of MDPF and fluorescamine XV chiroptical properties of MDPF condensation compounds with dipeptides in situ

2-Methoxy-2,4-diphenyl-3(2H)-furanone (MDPF) reacts readily with the free amino group of a dipeptide to form a pyrrolinone-type chromophore with absorption maxima at 275-285 and 370-390 nm. A simple test tube procedure is described which allows in situ correlation of the absolute configuration of the NH2-terminal amino acid of a dipeptide with the chiroptical properties of its chromophoric derivative. In several cases, unexpected deviation of the chiroptical characteristics from previously established empirical rules is observed.