A 2,3-diaminoporphyrin has been synthesised for the first time and its reaction with a-diones has been examined. Two regioselective routes to the precursor 2-amino-3-nitroporphyrins have been established. 2-Aminoporphyrins are directly nitrated on the porphyrin ring in the 3-position while 2-nitroporphyrins react with acylamide ions regioselectively at the 3-position and can be converted to the required 2-amino-3-nitroporphyrins by hydrolysis of the amide bond. 2,3-Diamino-5,10, 15,2O-tetraarylporphyrins are prepared by transfer hydrogenation of the corresponding 2-amino-3-nitroporphyrins but are relatively unstable. Electrochemical measurements show that 2,3-diaminoporphyrins are easily oxidised and this probably accounts for their instability. Condensation of the 2,3-diarninoporphyrin 29 with the a-diones benzil and cyclohexane-1,2-dione occurs readily and in good yield to give the ring annulated systems 31 and 32, respectively. Reaction with o-benzoquinone, however, causes decomposition of the diaminoporphyrin 29 making 'reverse' synthesis of quinoxalinoporphyrins and related polyporphyrin systems much less attractive than the alternate approach involving condensation of a porphyrin-2,3-dione with ophenylenediamine and related diamines.hrper 6/04245G

These results suggest that K-ras codon 12 mutations may occur frequently in patients with Barrett's oesophagus with high-grade dysplasia or adenocarcinoma of the oesophagus or oesophagogastric junction. K-ras mutation may be a late event in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence.

Quinoxalino[2,3-b]porphyrins are laterally-extended porphyrins with aromatic ring systems fused to the β,β'-positions of a pyrrolic ring of the macrocycle. They are building blocks for coplanar laterally-extended oligoporphyrins with applications in molecular electronics. The electrochemistry and spectroelectrochemistry of four such quinoxalinoporphyrins containing metal(II) ions and one free-base quinoxalinoporphyrin dissolved in nonaqueous media have been investigated and the data are compared to that seen for the same derivatives of the parent macrocycle lacking the fused quinoxaline ring. The investigated compounds are represented as (P)M and (PQ)M, where P = 5 ,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin, PQ = 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)quinoxalino[2,3-b]porphyrin and M = 2 H , Zn , Cu , Ni or Pd . The complexes all undergo two ring-centered reductions and one or two ring-centered oxidations in PhCN , CH 2 Cl 2, pyridine or THF . Additional redox reactions are also seen for the quinoxaline group in THF . The fusion of an electroactive quinoxaline group to the porphyrin macrocycle results in an 80 to 270 mV shift of E 1/2 towards easier reductions and the appearance of a third reduction which is assigned as a quinoxaline-centered redox process. The average HOMO-LUMO gap for the ( P ) M and ( PQ ) M derivatives is 2.26 ± 0.09 V and 2.14 ± 0.08 V , respectively. Both values are smaller than the average separation of 2.33 ± 0.13 V for the corresponding derivatives of tetraphenylporphyrin. The electrochemistry and UV-visible spectroelectrochemcal data indicate that moderate communication exists between the quinoxaline unit and the porphyrin π-ring system.

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