- Alcoholysis of naturally occurring imides: Misleading interpretation of antifungal activities
-
The frequent presence of the sulfur-containing amide penangin (10) in leaf extracts of Glycosmis species turned out to be the result of decomposition of imides generated by extraction and storage in MeOH. Reinvestigation of Glycosmis mauritiana and G. cf. puberula with acetone revealed the presence of six imides. In addition to penimides A (1) and B (2) and ritigalin (6), three new derivatives, krabin (4), isokrabin (5), and methoxypenimide B (3), were isolated and identified by spectroscopic methods. All six imides were shown to be susceptible to different rates of methanolic cleavage, leading to their corresponding methyl esters and sulfur-containing amides. Whereas the decomposition products penangin (10), isopenangin (11), and sinharin (14) are known, the corresponding cleavage of methyl N-methylthiocarbamate (7) from ritigalin (6), monitored in situ by 1H NMR spectroscopy, is described here for the first time. Its structure was further confirmed by GC-MS coupling. HPLC-UV comparison of many different samples of G. mauritiana, extracted with MeOH, revealed considerable chemical variations in sulfur-containing amides, strongly correlated with different antifungal potency. The lack of activity of many methanolic crude extracts can be explained by a preponderance of the inactive decomposition product penangin (10), whereas the corresponding naturally occurring imides penimides A (1) and B (2) and methoxypenimide B (3), extracted with acetone, showed high fungitoxic properties.
- Pacher, Thomas,Raninger, Adriane,Lorbeer, Eberhard,Brecker, Lothar,But, Paul Pui-Hay,Greger, Harald
-
scheme or table
p. 1389 - 1393
(2010/11/04)
-
- Preparation of mono-, di-, and trisubstituted ureas by carbonylation of aliphatic amines with S,S-dimethyl dithiocarbonate
-
General procedures are reported to prepare N-alkylureas, N,N′-dialkylureas (both symmetrical and unsymmetrical), and N,N,N′-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60°C with a molar ratio of DMDTC:amine = 1:2, preferably under nitrogen. Unsymmetrical ureas were prepared in two steps via S-methyl N-alkyl-thiocarbamate intermediates, which are formed selectively in the first step at room temperature. These intermediates react in the second step with ammonia or various aliphatic amines, both primary and secondary, at temperatures varying between 50 and 70°C. All the target ureas were obtained in high yields (28 examples, average yield 94%) and with very high purity (generally >99.2%). Also to be noted is the recovery of a co-product of industrial interest, methanethiol, in an amount of two moles for each mole of DMDTC, with complete exploitation of the reagent. Georg Thieme Verlag Stuttgart.
- Artuso, Emma,Degani, Iacopo,Fochi, Rita,Magistris, Claudio
-
p. 3497 - 3506
(2008/09/19)
-
- Conversion of carbonimidodithioates to carbamates
-
Carbonimidodithioates derived from primary amines or α-amino acid esters have been converted to N-benzyloxycarbonyl derivatives under mild conditions by treatment first with sodium benzyl alcoholate and then with water. N-Benzyloxycarbonyl α-amino acids have been generated from the methyl esters by alkaline hydrolysis or from the allyl esters by Pd0-catalysed de-allylation.
- Anbazhagan, Mariappan,Reddy, T. Indrasena,Rajappa, Srinivasachari
-
p. 1623 - 1627
(2007/10/03)
-
- Process for making alkyl N-alkyl or N-aryl-thiocarbamates
-
A process for the preparation of alkyl esters of N-alkyl or N-aryl thiocarbamic acid having the formula: STR1 wherein R is alkyl or aryl, R2 is alkyl and R1 is hydrogen or alkyl which comprises reacting the S-alkyl ester of N-alkyl or aryl dithiocarbamic acid having the formula: STR2 wherein R, R1, R2 have the meanings stated above with an appropriate alkali metal alkoxide in the presence of one or more alcoholic solvents.
- -
-
-