117486-31-4Relevant academic research and scientific papers
Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
Monenschein, Holger,Draeger, Gerald,Jung, Alexander,Kirschning, Andreas
, p. 2270 - 2280 (2007/10/03)
Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
A Catalytic Asymmetric Synthesis of N-Boc-β-Methylphenylalanines
Pasto, Mireia,Moyano, Albert,Pericas, Miquel A.,Riera, Antoni
, p. 8425 - 8431 (2007/10/03)
An efficient, stereodivergent, and enantioselective synthesis of the syn and anti diastereomers of N-Boc-β-methylphenylalanine has been developed. Starting from enantiomerically pure (2S,3S)-2,3-epoxy-3-phenyl-1-propanol, a three-step sequence, consisting of the oxidation of the primary alcohol up to the carboxyl stage, ring opening of the epoxy acid with Me2CuCNLi2, and esterification of the resulting hydroxy acid with methyl iodide, leads to the hydroxy ester anti-W, which has been converted in a stereodivergent manner into both the (2S,3R) and the (2R,3R) diastereomers of N-Boc-β-methylphenylalanine, syn-1 and anti-1, respectively. Activation of the secondary hydroxy group in anti-10 as a mesylate, followed by nucleophilic displacement with sodium azide, hydrogenolysis with simultaneous protection of the amino group, and saponification with LiOH, affords syn-1. The same reaction sequence applied to syn-10, obtained in turn by Mitsunobu reaction of anti-10 with p-nitrobenzoic acid followed by the hydrolysis of the resulting p-nitrobenzoate, leads to anti-1. Both products have been obtained with ≥99% enantiomeric excess.
Uncatalyzed and Chorismate Mutase Catalyzed Claisen Rearrangement of (Z)-9-Methylchorismic Acid
Lesuisse, Dominique,Berchtold, Glenn A.
, p. 4992 - 4997 (2007/10/02)
A synthesis of (-)- and (+/-)-(Z)-9-methylchorismic acid (3) is reported.The half-life for the uncatalyzed Claisen rearrangement of (+/-)-3 in H2O (pH 7.5, 30 deg C) is 5.7 h.Chorismate analogue (-)-3 was a modest substrate for chorismate mutase (chorismate mutase-prephenate dehydrogenase from E. coli): Km = 4.0 mM, kcat./kuncat. = 4.2*104.It was established that the enzyme-catalyzed Claisen rearrangement of (-)-3 proceeds through a chairlike transition state in similar fashion to the chorismate mutase catalyzed rearrangement of (-)-chorismic acid (1).
The Use of Microorganisms in Organic Synthesis. IV. Microbiological Asymmetric Reduction of Methyl 3-Phenyl 2-Oxobutyrate
Akita, Hiroyuki,Furuichi, Akiya,Koshiji, Hiroko,Horikoshi, Koki,Oishi, Takeshi
, p. 1342 - 1348 (2007/10/02)
The synthesis of optically active α-hydroxy β-methyl esters V by means of microbiological reduction of the corresponding α-keto β-methyl esters IV was carried out.Methyl 3-phenyl-2-oxobutyrate 3 was found to be reduced by a variety of yeasts to the α-hydr
