20182-99-4Relevant articles and documents
Influence of surface protonation-deprotonation stimulion the chiroptica l responses of (R)-/(S)-mercaptosuccinic acid-protected gold nanoclusters
Ueno, Ryota,Yao, Hiroshi
, p. 171 - 173 (2015)
Racemic mixtures of mercaptosuccinic acid (MSA) are opticall y resolved to obtain enantiopure (R)-/(S)-MSA, and the (R)-/(S)-MSA-protected gold nanoclusters are synthesized. Circular dichroism responses of the nanoclusters are strongly dependent on the pH of the solution. In particular, chiroptical enhancement is observed under highly acidic conditions, which can be due both to the electronic and conformational origins of the surface chiral MSA ligand.
Optical resolution of (RS)-mercaptosuccinic acid and syntheses of four stereoisomers of 2-amino-3-[(1,2-dicarboxyethyl)sulfanyl]propanoic acid
Shiraiwa, Tadashi,Ohkubo, Masanori,Kubo, Motoki,Miyazaki, Hideya,Takehata, Masaki,Izawa, Hisashi,Nakagawa, Kazuo,Kurokawa, Hidemoto
, p. 1364 - 1369 (1998)
To synthesize four stereoisomers of 2-amino-3-[(1,2- dicarboxyethyl)sulfanyl]propanoic acid (ADC), (RS)-mercaptosuccinic acid [(RS)-MSA] was optically resolved using (1S,2S)-2-amino-1-phenyl-1,3- propanediol and (R)- and (S)-1-phenylethylamine as resolving agents to yield (R)- and (S)-MSA with optical purities of 100%. In addition, the racemic structures of 1-propylammonium and 1-butylammonium salts of (RS)-MSA were examined based on melting point, solubility, infrared spectra, and binary and ternary phase diagrams, with the aim of optical resolution by preferential crystallization of (RS)-MSA. Results indicated that the 1-butylammonium salt of (RS)-MSA [(RS)-BA salt] exists as a conglomerate and that the 1- propylammonium salt forms a racemic compound. Optical resolution by preferential crystallization of (RS)-BA salt yielded (R)- and (S)-BA salts with optical purities of over 90%. The (R)- and (S)-MSA obtained by optical resolution were condensed with (R)- and (S)-2-amino-3-chloropropanoic acid hydrochlorides to give (2R,1'R)-, (2S,1'S)-, (2R,1'S)-, and (2S,1'R)-ADC. In addition, these stereoisomers were also synthesized from D- and L-cysteine and optically active bromosuccinic acid.
A new highly enantioselective synthesis of both (R)- and (S)-2- mercaptosuccinic acids
Chen, Bang-Chi,Bednarz, Mark S.,Kocy, Octavian R.,Sundeen, Joseph E.
, p. 1641 - 1644 (2007/10/03)
(R)- and (S)-2-Mercaptosuccinic acids 4 were prepared in five steps in >96% ee and 49-52% overall yield via a new efficient synthesis starting from commercially available L- and D-aspartic acids.
Thiomalate complexes of gold(I): Preparation, characterization and crystal structures of 1:2 gold to thiomalate complexes
LeBlanc, Daren J.,Smith, Richard W.,Wang, Zhixian,Howard-Lock, Helen E.,Lock, Colin J. L.
, p. 3263 - 3267 (2007/10/03)
The preparation and characterization of 1:2 gold to thiomalate complexes, as ammonium salts, has been described. The crystal structures of both racemic and optically pure samples are described and compared. In each case, the gold atom is linearly co-ordinated to two ligand sulfur atoms. Bond lengths and angles are normal.
Synthesis of (Racemization Prone) Optically Active Thiols by SN2 Substitution Using Cesium Thiocarboxylates
Strijtveen, Bert,Kellogg, Richard M.
, p. 3664 - 3671 (2007/10/02)
The cesium salt of thioacetic acid is prepared by treatment with cesium carbonate.This salt has a solubility of about 0.7 M in DMF (even higher in Me2SO) at 50 deg C.The mesylates of (R)-2-octanol, the ethyl ester and N,N-dimethyl amide of (R)-mandelic acid, (S)-ethyl lactate, (S)-methyl 3-phenyllactate, and (S)-diethyl malate underwent clean SN2 substitution in DMF solution.Racemization occured only in the case of the mesylate of ethyl mandelate when allowed to react in DMF, but complete inversion was achieved on use of absolute ethanol as solvent.Hydrolysis or aminolysis is used to deacylate the thiols (except for aliphatic thioacetates, which are deprotected by treatment with lithium aluminum hydride) to afford 2-mercapto esters or amides.Owing to the sensitivity of mercapto-bearing carbon, some racemization (0-20percent depending on the system) occurs during deprotection.An alternate route to the same materials prepared by the cesium thiocarboxylate method involves treatment of the free alcohol with thioacetic acid in the presence of twofold amount of the preformed salt from diisopropyl azodicarboxylate (DIAD) and triphenylphosphine.This method works well except for ethyl mandelate and N,N-dimethylmandelamide.Scale-up of the reaction is difficult, however, owing to the need for a chromatographic separation.Various NMR methods for determining the enantiomeric excesses of the various products are described.Particularly useful for determination of the high enantiomeric excesses is an internal calibration method based on the use of 13C satellite peaks in the presence of a chiral shift reagent.The enantiomeric excesses of the thiols were determined by conversion to the phosphonodithioates followed by measurement of the meso/d,l ratios obtained from 31P NMR spectra.Attempts to hydrolyze 2-acetylthio esters to the free 2-mercapto carboxylic acids lead to 10-40percent racemization depending on the compound.A partial solution to this problem was found by use of optically pure S bromides obtained from diazotation of (S)-alanine, (S)-phenylalanine, and (S)-valine in the presence of bromide.These bromides, on treatment with cesium thiobenzoate, underwent clean SN2 substitution, and debenzoylation could be brought about without significant racemization
