Epimerization and stereochemistry of avoparcin.
نویسندگان
چکیده
The epimerization of avoparcin entities is discussed in some detail. The absolute stereochemistry of avoparcin is now known since the N-methyl terminal amino acid of the aglycone has been isolated and shown to exhibit negative optical rotation and hence has the R-configuration. The same amino acid has been isolated from an epimerized solution of avoparcin and found to have positive rotation and hence the S-configuration. A comparison is made of the CD curves of beta-avoparcin and epi-beta-avoparcin. Some discussion on the effect of protonation of the terminal N-methyl group on the antibacterial activity of avoparcin is included.
منابع مشابه
Total synthesis of indole alkaloid alsmaphorazine D.
A concise total synthesis of rac-alsmaphorazine D has been described for the first time. The efficient synthetic strategy features four key transformations: 1) a catalytic intramolecular oxidative cyclization for the δ-lactamindole backbone; 2) an oxidative cyclic aminal formation for the hexahydropyrrolo[2,3-b]pyrrole framework; 3) a transannular radical cyclization for the construction of the...
متن کاملA macrolactonization approach to the total synthesis of the antimicrobial cyclic depsipeptide LI-F04a and diastereoisomeric analogues
The cyclic peptide core of the antifungal and antibiotic cyclic depsipeptide LI-F04a was synthesised by using a modified Yamaguchi macrolactonization approach. Alternative methods of macrolactonization (e.g., Corey-Nicolaou) resulted in significant epimerization of the C-terminal amino acid during the cyclization reaction. The D-stereochemistry of the alanine residue in the naturally occurring ...
متن کاملpH-Driven dynamic stereoinduction: epimerization upon dimerization in rhenium(I) complexes.
Stereochemistry at the metal centre in a Re(I) complex can be modified by manipulating the pH: while acidic conditions favour a monomeric system, basic conditions induce a dimerization which concomitantly epimerizes the metal centre.
متن کاملActivities and Antagonism between Natural and Synthetic Analogs
The importance of the two chiral centers at C-3 and C-7 in the molecular structure of jasmonic acid in plant responses was investigated. We separated methyl jasmonate (MeJA) into (3R)and (3S)-isomers with a fixed stereochemistry at (2-3, but epimerization at C-7 i s possible. The four isomers of the nonepimerizable analog 7-methyl MeJA were synthesized. These six esters and their corresponding ...
متن کاملSynthesis and thermotropic phase behavior of four glycoglycerolipids.
Four glycoglycerolipids with different head groups have been synthesized and their physicochemical properties studied. The lengths of the head groups from a mono-saccharide to a trisaccharide, in addition to the anomeric stereochemistry for the smaller glycoglycerolipids, have been modified. The synthesis has been optimized to avoid glycerol epimerization and to allow up-scaling. The physicoche...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- The Journal of antibiotics
دوره 36 12 شماره
صفحات -
تاریخ انتشار 1983