René Beugelmans

Reductive deprotection of aryl allyl ethers with Pd(Ph3)4/NaBH4

Treatment of aryl allyl ethers with catalytic amts. of Pd(PPh3)4 and NaBH4 at room temp. afforded the parent phenol in high yield under non-hydrolytic conditions. E.g., treatment of ether I (R = allyl) with NaBH4 in the presence of Pd(PPh3)4 in THF gave 97% I (R = H). [on SciFinder (R)]

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.

A novel synthesis of K-13

A new and concise synthesis of the 17-membered macrocyclic tripeptide K-13 is achieved featuring an intramol. SNAr reaction as a key step. [on SciFinder (R)]

A new access to 14-membered macrocycle: Synthesis of model F-O-G ring of teicoplanin

A new strategy based upon the intramol. SNAr reaction was developed for the synthesis of I, the 14-membered F-O-G macrocyclic ring system of teicoplanin. Thus, treatment of acyclic precursor II (X = F) with CsF or K2CO3/18-crown-6 in DMF at room temp. for 6-20 h gave 62-82% I. Chloride II (R = Cl) gave 80% I on treatment with K2CO3 in DMF at 80 Deg for 6 h. The reason for the easy macrocyclization was advanced and supported by computational studies. [on SciFinder (R)]

Action de l'hydroxylamine, de l'hydrazine et de ses derives sur les γ-pyrones

Abstract The reaction of hydroxylamine and hydrazine on γ pyrones was generally reported to yield various heterocycles in which nitrogen is incorporated. More recently, several authors have reported that γ-pyrones oximes and hydrazone derivatives can be obtained and have settled some controversial previous results. This report presents a review of this question.

Synthesis of a modified carboxylate-binding pocket of vancomycin

A 16-membered tetrapeptide macrocycle I, an analog of the vancomycin binding pocket, has been designed and synthesized using the efficient macrocyclization of the corresponding linear tetrapeptide via biaryl ether formation. In acetone, I adopted a right conformation needed for binding carboxylate anion even in the absence of -Ac-D-Ala-D-Ala-OH. [on SciFinder (R)]

An easy access to functionalized diaryl ethers: formal total synthesis of K-13

As an alternative to the Ullmann ether synthesis, the SNAr reaction led to an efficient one step synthesis of chiral bis-amino acid diaryl ethers, e.g. the reaction of 2-FC6H4NO2 with tyrosine deriv. Boc-Tyr-OMe in the presence of base gave diaryl ether I. The above diaryl ethers are important intermediates in the synthesis of K-13 II. [on SciFinder (R)]

Phenoxide and naphthoxide ions as nucleophiles for SRN1 reactions: Synthesis of biphenyl and phenylnaphthyl derivatives

Abstract Biphenyl or phenylnaphthyl derivatives are obtained by photostimulated SRN1 reactions between the anion of phenols or naphthols and variously substituted haloarenes.

Chemoenzymatic synthesis of enantiomerically pure 4-fluoro-3-nitro and 3-fluoro-4-nitro phenylalanine

Enantiomerically pure L- and D-4-fluoro-3-nitrophenylalanines and L- and D-3-fluoro-4-nitrophenylalanines were obtained from their corresponding racemates via enzymic resoln. [on SciFinder (R)]

Synthesis of hapalosin and 8-deoxy-hapalosin

Hapalosin, a new MDR reversing agent, and its congener 8-deoxyhapalosin have been synthesized via macrolactamization. A new procedure for selective N-methylation of a vicinal amino alc. is uncovered in the course of this study. [on SciFinder (R)]