Bernard Chantegrel

4-Oxo-1H-and-2H-[1]benzopyrano[4,3-c]pyrazoles. Preparation from 4-hydroxycoumarin or 3-chromonecarboxylic acid derivatives.

Abstract The conversion of 3-acyl-4-hydroxycoumarins to either 4-oxo-1-phenyl-1H-[1]benzopyrano[4,3-c]pyrazoles 2 or 4-oxo-2-phenyl-2H-[1]benzopyrano[4,3-c]pyrazoles 3 is described. The product obtained from the reaction of phenylhydrazine with 3-chromonecarboxylic acid 6a has been established not to be such 2-phenyl[1]benzopyrano[4,3-c]pyrazol-3-2H-one 7 as previously reported but to be 4-oxo-1-phenyl-1H[1]benzopyrano[4,3-c]pyrazole 2a . Our results showed evidence that the method precedently described as yielding 2a , from 4-chloro-3-formyl-coumarin was an implausible one.

Contribution of 4-methylthio-2-oxobutanoate and its transaminase to the growth of methionine-dependent cells in culture: Effect of transaminase inhibitors

The growth in culture of methionine-dependent transformed cells of human, rat and mouse origin was arrested in the absence of L-methionine (Met) but took place in the presence of 4-methylthio-2-oxobutanoic acid (MTOB), the keto acid of Met. From 24 hr after seeding, cells grew in 0.1 mM MTOB medium at a rate comparable to that in 0.1 mM Met medium. Using [35S]MTOB, it was found that the Met synthesized was used in normal MRC-5 cells and in transformed HeLa cells to the same extent for protein, adenosylmethionine and adenosylhomocysteine syntheses. However, when the free Met content was examined, it was found to be 3-fold greater in HeLa than in MRC-5 cells. To examine the importance of this free Met for the growth of transformed cells, the transaminase responsible for converting MTOB to Met was chosen as a target enzyme for the synthesis of compounds with potential inhibitory activity. Since this is a multisubstrate enzyme, reduced Schiff bases were prepared containing both pyridoxal or other aromatic groups, as one constituent, and L-Met or other amino-acids in the free acid or ester or amide form, as the other constituent. Only esters containing the pyridoxal moiety and Met or certain of its structural analogues exhibited good selective growth inhibitory activity in that there was little (20%) or no effect on the growth of normal MRC-5 and derm cells, respectively, while that of transformed HeLa, HEp-2 and L1210 cells was strongly inhibited (80%). This inhibition was accompanied by a concomitant decrease in the activity of the MTOB transaminase in both HeLa and MRC-5 cells treated with 3c the most potent inhibitor. However, using [35S]MTOB it was found that MTOB itself accumulated 48% in HeLa but only 12% in MRC-5 cells treated with 3c. On the contrary [35S]Met formed from [35S]MTOB increased 3.7-fold in MRC-5 inhibitor-treated cells showing 20% growth inhibition whereas it decreased 38% in HeLa-treated cells showing 80% growth inhibition. This decrease in cellular Met in HeLa is not responsible for growth arrest. Indeed the growth of HeLa cells could not be restored by adding a 10-fold excess of Met. Since MTOB can alleviate Met-dependence, the intracellular homeostasis of this metabolite may play a hitherto unsuspected role in controlling cell growth.

Tandem Wolff rearrangement-“α-cyclization of tertiary amines” sequence: Synthesis of some 1H-2-benzopyran derivatives

Abstract The thermolyses of dimethyl 1-diazo-2-oxo(2-(N,N-disubstituted aminomethyl)phenyl)-ethylphosphonates6a-e or the related ester 6f afford 1-disubstituted amino-1H-2-benzopyran derivatives 9a-f through a 3-step sequence involving Wolff rearrangement, [1,5] hydride shift and subsequent ring closure. Compounds 9 can be easily transformed into 1-hydroxy-, 1-methoxy- or 1-thiophenoxy-1H-2-benzopyran or isoquinoline derivatives by the action of various nucleophilic reagents. Extension of the reaction to some heterocyclic diazophosphonates analogous to 6 is also described.

Chemoselectivity in the rhodium(II) acetate catalysed decomposition of α-diazo-β-keto-γ,δ-alkenyl-δ-aryl compounds: Aromatic C-H insertion reaction or wolff rearrangement-electrocyclization

Abstract The rhodium(II) acetate catalysed decomposition of α-diazo-β-keto-γ,δ-alkenyl phosphonates 1 substituted in the δ-position by an aryl group gave rise to mixtures of isomeric hydroxynaphthalenephosphonates, 3 resulting from a Wolff rearrangement-electrocyclization process and 5 resulting from an aromatic C-H insertion reaction. The 3:5 ratio was found to depend on the substitution pattern of the γ,δ-double bond. The diazoesters 9 which are the analogs of diazophosphonates 1 showed similar behaviour. In particular the rhodium(II) acetate catalysed decomposition of ethyl 2-diazo-5,5-diphenyl-3-oxopent-4-enoate 9c led to ethyl 1-hydroxy-4-phenyl-2-naphthalenecarboxylate 11c and not to ethyl 2-hydroxy-4-phenyl-1-naphthalenecarboxylate 10c as previously reported. The structure of 11c was confirmed by X-ray crystallography.

Tandem wolff rearrangement-“tert-amino effect” sequence: Synthesis of 2-oxoindolinium enolate and 1H-2-benzopyrane derivatives.

Abstract The thermal decomposition of dimethyl 1-diazo-2-oxo-(2-N,N-disubstituted aminophenyl)ethylpnosphonates 1 gave rise to 2-oxoindolinium enolates 3 resulting from a Wolff rearrangement followed by an attack of the nitrogen atom on the intermediate ketene moiety. Ammonium ylides 5 resulting from the decomposition of 1 were also formed through a carbene path. The thermal decomposition of dimethyl 1-diazo-2-oxo-(2-(N,N-disubstituted aminomethyl)phenyl) ethylphosphonates 6 followed a different course and afforded 1 H -2-benzopyranes 9 as the sole isolated products through a Wolff rearrangement — [1,5] H shift — ring closure sequence. The structures of 3a and 5a were confirmed by X-ray crystallography.

TANDEM WOLFF REARRANGEMENT- TERT-AMINO EFFECT SEQUENCE : SYNTHESIS OF 2-OXOINDOLINIUM ENOLATE DERIVATIVES

Abstract The thermolysis of 1-diazo-2-oxo-(2-N,N-disubstituted aminophenyl)ethylphosphonates 1 gave rise to 2-oxoindolinium enolate derivatives 4 through Wolff rearrangement and interaction of the tert-amino moiety with the ketene functionality. Variable amounts of either ammonium ylides 5 or of products resulting from their transformations were also formed during the course of the reaction. If the amino moiety was substituted by a benzyl or an allyl group, indolinones, resulting from [1,3] or [1,2] benzylic or allylic shifts, were isolated in place of compounds 4 and 5.

Synthesis of sodium salt of ortho-(difluoromethyl)phenyl-α-ketoside of N-acetylneuraminic acid : a mechanism-based inhibitor of Clostridium perfringens neuraminidase.

Abstract The title compound 7 was prepared in seven steps from N-acetylneuraminic acid and proven to be an enzyme-activated irreversible inhibitor of Clostridium perfringens neuraminidase. Title compound 7 was prepared in seven steps from N-Acetylneuraminic acid and proven to be an enzyme-activated irreversible inhibitor of Clostridium perfringens neuraminidase.

Reaction of Trifluoroacetic Anhydride with N-(2-Hydroxybenzyl)-a-amino Acids: An Entry in the New [1,3]Oxazolo[2,3-b][1,3]benzoxazine Ring System

The diastereospecific double ring closure of N-(2-hydroxybenzyl)-α-amino acids with trifluoroacetic anhydride leads to the formation of 10a-trifluoromethyl-2,3,4,10a-tetrahydro-[1,3]oxazolo[2,3-b][1,3]benzoxazin-2(5H)-ones. The chemical structures are supported by ir, 1 H-nmr and 13 C-nmr spectra and X-ray analysis