The use of porphyrins in fundamental studies and diverse applications requires facile access to ample quantities of material in pure form. The existing conditions for the condensation of a dipyrromethane plus a dipyrromethane-dicarbinol employ 2.5 mM reactants and afford ∼30% yields with no detectable scrambling. Large-scale syntheses require condensation and oxidation conditions that function at higher concentrations. Thirty-one acids (plus additives) have been examined for reactions at 25 mM reactants using the synthesis of a trans-A 2 B 2 -porphyrin as a model. The porphyrin was formed in ∼20% yield upon condensation in CH 2 Cl 2 at room temperature using ( 1) Sc(OTf) 3 (3.2 mM) + 2,6-di-tert-butylpyridine (32 mM), or (2) Zn(OTf) 2 (10 mM). Nine porphyrins were prepared in this manner in yields of 15-22% with no detectable scrambling, whereas three other porphyrins afforded low levels of scrambling and/or lower yields (8-14%). Conditions for the oxidation also have been investigated. The reaction of 5-mesityldipyrromethane and the dicarbinol derived from 1-(4methoxybenzoyl)-9-(4-methylbenzoyl)-5-phenyldipyrromethane (18 mmol each in 720 mL of CH 2 Cl 2 ; 25 mM) with catalysis by Sc(OTf) 3 /2,6-di-tert-butylpyridine and aerobic oxidation [(t-Bu 4 FePc) 2 O and DDQ, 2.5 mol % each with a stream of O 2 ] afforded 2.88 g (22.8% yield) of the corresponding ABCD-porphyrin. The present synthesis (25 mM), at 4.5-times larger scale than the largest prior analogous synthesis (2.5 mM reactants with stoichiometric use of DDQ), afforded 4.0 times as much porphyrin on a molar basis while employing about one-half the amount of solvent and < 1 / 25 the amount of DDQ. A three-step one-flask process also was developed that employs (i) condensation at 25 mM reactants, (ii) aerobic oxidation, and (iii) metal insertion to afford the metalloporphyrin [Mg(II), Ni-(II), Cu(II), Zn(II), Pd(II)] in a streamlined manner. Taken together, the various improvements facilitate gram-scale syntheses of diverse porphyrins.

1,9-Diacyldipyrromethanes are important precursors to porphyrins, yet synthetic access remains limited owing to (1) poor conversion in the 9-acylation of 1-acyldipyrromethanes and (2) handling difficulties because acyldipyrromethanes typically streak upon chromatography and give amorphous powders upon attempted crystallization. A reliable means for converting a dipyrromethane to a 1-acyldipyrromethane-dialkylboron complex was recently developed, where the dialkylboron (BR(2)) unit renders the complex hydrophobic and thereby facilitates isolation. Herein a refined preparation of 1,9-diacyldipyrromethanes is presented that employs the 1-acyldipyrromethane-BR(2) complex as a substrate for 9-acylation. The dialkylboron unit provides protection for the alpha-acylpyrrole unit. 9-Acylation requires formation of the pyrrolyl-MgBr reagent and the presence of 1 equiv of a nonnucleophilic base to quench the proton liberated upon alpha-acylation. Reaction of the 1-acyldipyrromethane-BR(2) complex (1 equiv) with mesitylmagnesium bromide (2 equiv) followed by the addition of an acylating agent (S-2-pyridyl thioate or acid chloride, 1.1 equiv) gives the corresponding 1,9-diacyldipyrromethane-BR(2) complex. The acylation method afforded 1,9-diacyldipyrromethane-BR(2) complexes with limited or no chromatography in yields of 64-92%. The 1,9-diacyldipyrromethane-BR(2) complexes are stable to routine handling, are readily soluble in common organic solvents, crystallize readily, and can now be prepared in multigram quantities through use of stoichiometric quantities of reagents.

A new strategy for preparing porphyrins that bear up to four different meso-substituents (ABCD-porphyrins) relies on two key reactions. One key reaction entails a directed synthesis of a 1-protected 19-acylbilane by acid-catalyzed condensation at high concentration (0.5 M) of a 1-acyldipyrromethane and a 9-protected dipyrromethane-1-carbinol (derived from a 9-protected 1-acyldipyrromethane). Three protecting groups (X) were examined, including thiocyanato, ethylthio, and bromo, of which bromo proved most effective. The bilanes were obtained in 72-80% yield, fully characterized, and examined by 15N NMR spectroscopy. The second key reaction entails a one-flask transformation of the 1-protected 19-acylbilane under basic, metal-templating conditions to give the corresponding metalloporphyrin. The reaction parameters investigated for cyclization of the bilane include solvent, metal salt, base, concentration, temperature, atmosphere, and time. The best conditions entailed the 1-bromo-19-acylbilane at 100 mM in toluene containing DBU (10 mol equiv) and MgBr2 (3 mol equiv) at 115 degrees C exposed to air for 2 h, which afforded the magnesium porphyrin in 65% yield. The magnesium porphyrin is readily demetalated to give the free base porphyrin. A stepwise procedure (which entailed treatment of the 1-(ethylthio)-19-acylbilane to oxidation, metal complexation, desulfurization, carbonyl reduction, and acid-catalyzed condensation) was developed but was much less efficient than the one-flask process. The new route to ABCD-porphyrins retains the desirable features of the existing "2 + 2" (dipyrromethane + dipyrromethane-1,9-dicarbinol) method, such as absence of scrambling, yet has significant advantages. The advantages include the absence of acid in the porphyrin-forming step, the use of a metal template for cyclization, the ability to carry out the reaction at high concentration, the lack of a quinone oxidant, avoidance of use of dichloromethane, and the increased yield of macrocycle formation to give the target ABCD-metalloporphyrin.

Rational routes to synthetic porphyrins bearing distinct mesosubstituents have typically been implemented at modest scale (<1 g quantities). The A 3 B-porphyrin 5-(4-hydroxymethylphenyl)-10,15,20-tri-p-tolylporphinatozinc(II) (Zn-1) is required in multigram quantities for possible commercial use in information storage applications. The synthesis of Zn-1 has been carried out by reaction of 5-(4-hydroxymethylphenyl)dipyrromethane and the dicarbinol derived from 1,9-di-p-toluoyl-5-p-tolyldipyrromethane. Four improvements have been made to the steps leading to the dipyrromethane and dipyrromethane-dicarbinol: (i) use of 50 equiv of pyrrole in the condensation of an aldehyde to give the dipyrromethane (versus 100 equiv previously), (ii) 1,9-diacylation of a dipyrromethane using the hindered Grignard reagent 2,6-dimethylphenylmagnesium bromide and p-toluoyl chloride to give the 1,9-diacyl versus 1-acyl products in >10:1 ratio (versus 4:1 using EtMgBr), (iii) isolation of the dibutyltin complex of the 1,9-diacyldipyrromethane from the crude reaction mixture by direct crystallization using methanol/methyl tert-butyl ether (MTBE) (versus silica chromatography), and (iv) reduction of the dibutyltin complex of the 1,9-diacyldipyrromethane (250 mM) with ∼10-15 mol equiv of NaBH 4 (versus 25 mM and 40 mol equiv). The procedures have been carried out with no chromatography at large scale, affording the dipyrromethane (31, 59, or 79 g), the dibutyltin complex of a 1,9-diacyldipyrromethane (361 g), and reduction of the latter (45 g). The porphyrin-forming reaction has been performed (25 mM reactants at 50-mmol scale, or 10 mM at 64-mmol scale) in a two-step process of condensation and oxidation to give the free base porphyrin 1 in 3.7-or 5.8-g quantities. Metalation with zinc acetate afforded Zn-1, which was isolated by direct crystallization. Taken together, the various improvements facilitate synthesis of the target porphyrin Zn-1 and may have broad applicability.

in silico modeling, using Psipred and ExPASy servers was employed to determine the structural elements of Bcr-Abl oncoprotein (p210BCR-ABL) isoforms, b2a2 and b3a2, expressed in Chronic Myelogenous Leukemia (CML). Both these proteins are tyrosine kinases having masses of 210-kDa and differing only by 25 amino acids coded by the b3 exonand an amino acidsubstitution (Glu903Asp). The secondary structure elements of the two proteins show differences in five α-helices and nine β-strands which relates to differences in the SH3, SH2, SH1 and DNA-binding domains. These differences can result in different roles played by the two isoforms in mediating signal transduction during the course of CML.