Jacqueline Chastanet

Palladium catalyzed reductive deprotection of alloc: Transprotection and peptide bond formation

N-allyloxycarbonyl group could be efficiently removed using sodium borohydride as hydride donor in the presence of catalytic amount of palladium (0). The conditions were applied to chemoselective protecting group transformation (transprotection) and peptide bond formation.

Asymmetric synthesis of (2S,3R) β-(4-F-3-NO2) phenyl serine, D-(R)-4-methoxy-3,5-bistbutyldimethylsiloxy phenylglycine and their assemblage to C-O-D ring of vancomycin

The asym. synthesis of two appropriately functionalized nonproteinogenic amino acids I (Troc = CO2CH2CCl3, TBS = SiMe2CMe3) and II (Boc = Me3CO2C) needed for the total synthesis of vancomycin is described. The assemblage of these amino acids into linear tripeptide followed by biaryl ether formation via intramol. SNAr reaction led to the fully functionalized C-O-D ring III of vancomycin. [on SciFinder (R)]

A HIGHLY STEREOSELECTIVE SYNTHESIS OF (2S, 3S)-BETA -HYDROXYLEUCINE

An efficient asym. synthesis of (2S,3S)-beta -hydroxyleucine is described. The key step in the synthesis was a highly diastereoselective nucleophilic addn. of Grignard reagent to N,N-dibenzyl-O-TBS-serinal (TBS = SiMe2CMe3). This strategy should be applicable to the synthesis of other related beta -hydroxy amino acids. [on SciFinder (R)]

Studies on SRN1 reactions-9 : A new access to the isoquinoline ring system☆

Abstract The SRN1 reaction between o-halogeno-benzylamines and enolates derived from a series of ketones and aldehydes affords 1, 2 dihydro-isoquinolines from which are obtained (i)the isoquinoline derivatives, either spontaneously or by treatment on Pd-C and (ii) the 1,2,3,4 tetrahydro-isoquinoline derivatives after sodium borohydride reduction.

Synthesis of fluorinated biaryl derivatives via SRN1 reactions

Abstract Flourinated biaryl derivatives Y-C 6 -H 4 -ArOH (Y = F, CF 3 , OCF 3 ) are obtained by coupling Y-C 6 -H 4 -Br(p) with anions derived from ArOH via a photostimulated S RN 1 reaction.

SRN1 reactions of chlorotrifluoromethyl pyridines with naphtholate, phenolate and malonate anions

Abstract - 2-Chloropyridines, bearing a CF 3 group on position 3, 4, 5 or 6 (2-Cl Py CF 3 ) were found to be suitable substrates for photostimulated S RN 1 reactions with nucleophiles derived from 2-naphthol (Nap-OH) or from phenol (PhOH). Carbon-carbon coupling between the regiospecifically generated 2-pyridyl radical and the carbanionic site of the nucleophile yields 2-heterobiaryl derivatives (CF 3 Py-Nap-OH or CF 3 Py-PhOH). Similarly, coupling of the 2-amino-5-CF 3- 3-pyridyl radical yields 3-heterobiaryl derivatives. Coupling of the malonate anion takes place with the aforementioned radicals.

Synthesis of various substituted dibenzo[b,d]pyranones including amino acid derivatives by SRN1 methodology

An easy prepn. of the title compds. involving a SRN1 o-arylation of phenolates by o-bromobenzonitrile followed by SiO2-catalyzed lactonization is described. Activated or not activated phenols are efficient. Access to benzonaphthopyranones is exemplified by the reactions with 2-naphtholate. Reactions with chiral p-hydroxyphenylamino acid derivs. are also reported. Thus, irradn. of Ac-L-Tyr(Ac)-OMe and 2-bromo-4,5-dimethoxybenzonitrile in liq. NH3, followed by treatment with silica in CH2Cl2, gave 52% dibenzopyranyl amino ester I. [on SciFinder (R)]

Selective hydroxy group protection of gallic acid

Abstract An efficient procedure allowing selective differentiation of the 4-hydroxy group of methyl gallate was reported.

[3+2] Cycloaddition of chiral, azomethine ylides from aminosugar N-oxides. Enantioselective synthesis of 3,4-disubstituted pyrrolidines

The base deprotonation method, applied to amino-sugar N-oxides preparcd from methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside (8) and methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (9), allows the easy generation of complex and very reactive sugar azomethine ylides. Fair yields of the major diastereomeric pyrrolidines resulting from [3+2] cycloaddition to stilbene are thus obtained with good asymmetric induction. The easy elimination of the chiral appendage as starting epoxides gives access to the enantiomerically enriched 3,4-diphenylpyrrolidines