A Reinvestigation of the Configuration of Hemin¹

N‐methylporphyrins

“…In addition to the shifts observed it will be noted that changes occur in the multiplicity and relative positions of the meso-proton resonances; these were, there- fore, investigated by a series of spectroscopic titrations (FIGURE 9) in which the monocationic species in deuterochloroform was converted into the dicationic species by successive additions of small amounts of TFA. The highest field, signal assigned to the a-proton, moves to lowest field, slowly at first and then more rapidly while the Band 6-proton resonances show similar but less pronounced shifts, and the two curves cross over; the remaining signal due to the y-proton moves slightly to higher field initially, then falls again.…”

“…However, further treatment of the AB isomer with methyl fluorosulphonate resulted in a product presumed to be the N,NbN,-trimethyloctaethylporphyrin (ll), although it decomposed on attempted purification by chromatography. On the basis of these results, it seems likely that the more sterically strained cis-N,Nb-dimethyl porphyrin (9) is formed by decomposition of the N,N,N-trimethyl compound (ll), whereas the trans-N.N,-dimethylporphyrin (10) is formed (like the trans-AB isomer) by direct methylation of the N-monomethylporphyrin.…”

“…The dimethyl-porphyrin decomposed on heating to give mixtures of the N-methyl porphyrin and the parent porphyrin. The Nottingham group also studied the methylation of octaethylporphyrin with methyl fluorosulphonate; at room temperature in chloroform solution the N-methyl-and N.Nb-dimethyl derivatives were formed, but in boiling chloroform the cis-N,N,-dimethyl porphyrin (9) was also obtained. The AB isomer was not transformed into either of the AC isomers on heating in boiling chloroform, thus showing that interconversion was not occurring.…”

Synthesis of potential prodrug systems for reductive activation. Prodrugs for anti-angiogenic isoflavones and VEGF receptor tyrosine kinase inhibitory oxindoles

“…An analogous set of derivatives 24-29 was prepared from SU5416 16, obtained from condensation of oxindole with 3,5-dimethylpyrrole-2-caboxaldehyde, 45 using similar protocols, as outlined in Scheme 3. No attempt was made to optimize the rather poor yields observed in some of these coupling reactions.…”

Oxindole as starting material in organic synthesis

“…Semaxinib 43 has been synthesized by the reaction between oxindole and 3,5-dimethylpyrrole-2-carboxaldehyde 42, 94 as described before. 33 An analogous set of compounds 226, 227 and 228 was prepared from Semaxanib as outlined in Scheme 70.…”