Isobacteriochlorins synthesis

Isay reaction, 2, 79-80 3, 259 Ismelin 7, 656 Isoalloxazine oxidation states, 1, 252 Isoaminopterin synthesis, 3, 327 Isoarsindolines, 1, 543-544 Isoarsinoline, tetrahydro-synthesis, 1, 552-553 stability, 1, 552 Isoascorbic acid structure, 4, 552 ( )-IsoavenacioIide synthesis, 1, 416 Isoazapenem synthesis, 1, 465 Isobacteriochlorin synthesis, 4, 419 Isobacteriochlorin, dimethyl-biosynthesis, 1, 105 Isobacteriochlorin, methyl-biosynthesis, 1, 105 Isobacteriochlorin, trimethyl-biosynthesis, 1, 105 Isobarbituric acid Mannich reaction, 3, 71 synthesis, 3, 133... 

Synthesis of chlorins, bacteriochlorins, isobacteriochlorins, and higher reduced porphyrins 98PHC1. 

The important biological role of the isobacteriochlorins has decisively influenced the development of synthetic approaches leading to the isobacteriochlorin class of compounds. All of the naturally occurring isobacteriochlorins contain geminally dialkylated structural parts in the saturated pyrrole rings, which require special approaches for their synthesis. Until the discovery of siroheme and sirohydrochlorin, this structural element could only be found in vitamin B,2. Using the synthetic potential, which was invented during numerous syntheses of... 

In the above route, zinc(II) can be replaced by other metal ions such as copper(II) and nickel(II). The pinacol approach to isobacteriochlorins has also been successfully applied to the synthesis of heme dj. 20a b... 

The modification of porphyrins leading to isobacteriochlorins by C —C-bond formation is important to obtain a wide range of structurally different isobacteriochlorins which can then be further transformed. Protoporphyrin, deutoroporphyrin and hematoporphyrin (readily accessible from red blood pigment) are interesting and useful starting materials in the synthesis of isobacteriochlorins. 

Oxidation reactions were used in the synthesis of porphyrin d, the metal-free ligand system of naturally occurring heme d,. In a total synthesis of porphyrin d,12d oxo functions were introduced into isobacteriochlorin 3 by selenium dioxide oxidation to yield 4. The selenium dioxide selectively attacks the 3- and 8-positions of the partially reduced pyrrole rings of the chromophore. In another synthesis23a c of porphyrin d, an isobacteriochlorin 5, derived by... 

The tautomerization of porphyrinogens to pyrrocorphins has been reported in detail in connection with the synthesis of chlorins (sec Section 1.2.1.3.), baeteriochlorins (see Section 1.3.1.) and isobacteriochlorins (see Section 1.4.1.3.). Therefore, only the porphyrinogen-pyrrocorphin tautomerization of uroporphyrinogen I octacarbonitrile 8- 96 will be described as it is of importance regarding the biosynthesis and a possible prebiotic formation of corrins.la,b-2 A major problem concerned with using this approach synthetically is the number of possible diastereomeric products (4 in a 1 1 1 1 ratio) obtained in the reaction and also the formation of isobacteriochlorin diastereomers 10. 

Reaction of porphyrins with nitrones has also been studied and the results obtained showed that this is a versatile approach leading to the synthesis of isoxazolidine fused-chlorins (Scheme 26). For instance, chlorin 74 was successfully prepared from the reaction of the jV-methylnitrone, generated in situ from JV-methyl hydroxylamine and paraformaldehyde, with porphyrin Id . It is important to note that bis-addition also took place, yielding exclusively bacteriochlorin type derivatives 76 and 77 (Figure 6). This result contrasts with those obtained in 1,3-DC reactions with azomethinic ylides where isobacteriochlorins were obtained preferentially. 

C,D-Tetradehydrocorrins have been prepared during the studies on the synthesis of isobacteriochlorins [74], They represent the only example of reduced corrins isolated as metal-free ligands. 

Reduction of the porphyrin 7t-system results in a bathochromic shift and an enhancement of the extinction coefficient of the Q-band. There are characteristic differences between bacteriochlorins and isobacteriochlorins. An ultraviolet spectrum of a pyrrocorphin (15) has been described, proving earlier reports on a synthesis of this compound to be erroneous (85CC1604). 

A sigmatropic methyl shift from an angular to a meso position (Scheme 19) is the crucial step in synthesis of the isobacteriochlorin 137 and the pyrrocorphin 138 (83CC1401). 

Synthesis and characterization of other related macrocycles, including chlorins, " isobacteriochlorins, bacteriochlorins, mono- and dioxoporphyrins, " other more highly saturated hydroporphyrins, N-alkyl- or A-arylporphyrins, some of which are chiral, porphodimethenes, thiaporphyrins, " oxaporphyrins, N-confused " and carbapor-phyrins, porphycenes " and corrphycenes, " tetraazaporphyrins, phthalocyanines, the ring-expanded sapphyrins, texaphyrins and others, and the ring-contracted corroles " and corrolazines have also been synthesized and are discussed in the indicated references. 

Cyclization to the benzo[c]phenanthridine (127) competes with rearrangement to the ring-expanded product (128) on irradiation of the amine oxide (129). A practical synthesis of the chlorin macrocycle (130) has been developed by irradiation of the seco-compound (131) in tetrahydrofuran containing TFA and Hiinig s base this is thought to take place by photocyc-lization of the ISrr-tautomer (132), followed by elimination of methanol. Analogous approaches have been employed in the syntheses of ( )-bonellin dimethyl ester and 20-methyl- and 20-cyano-isobacteriochlorins. " ... 

The Synthesis of Chlorins, Bacteriochlorins, Isobacteriochlorins and Higher Reduced Porphyrins... 

Acidic cleavage of the /ert-butyoxycarbonyl group, which has served to keep the enamine double bond of rac-88 in the exocyclic position, completes the synthesis of isobacteriochlorin 93. A very similar concept has made it possible to synthesize a symmetric isobacteriochlorin <90AG(E)43> and in a modified synthetic approach the isobacteriochlorin 93 was obtained by coupling the AB- and CD-building blocks by a sulfide contraction procedure <81HCA1431>. 

Chang and Fajer have also recently completed a synthesis of a model isobacteriochlorin (101), although their approach will not be applicable to the natural product itself. The approach rests on Inhoffen s earlier syntheses of the bisgeminiketone (102) by treatment of octaethylporphyrin with hydrogen peroxide in acid. This compound was then treated with methylithium to give the tertiary alcohol (103), which was subsequently reduced with HI/H3PO2/AC2O and afforded the required isobacteriochlorin (101). 

C. K. Chang, Synthesis and characterisation of alkylated isobacteriochlorin models of sitoheme and sirohydrochlorin, Biochemistry, 19, 1971 (1980). 

R is the 5,22-dihydro- porphyrin skeleton isomeric to chlorin in which the conjugation is interrupted it plays a role in the biosynthesis of porphyrin and the total synthesis of chlorophyll. Close relatives of P. are the porphomethenes in which the conjugation is also interrupted and which represent to the bacteriochlo-rins and isobacteriochlorins isomeric tetrahydropor-... 

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