Synthesis and properties of homomologated and contracted dipyrrinone analogs of xanthobilirubic acid

Abstract

Dipyrrinone analogs of xanthobilirubic acid, 5‐[1,5‐didehydro‐3‐ethyl‐4‐methyl‐5‐oxo‐2H‐pyrrol‐2‐ylidene)‐methyl]‐2,4‐dimethyl‐1H‐pyrrol‐3‐propanoic acid, with alkanoic acid chain lengths varying from formic to caproic have been synthesized as their methyl esters and characterized spectroscopically. All of the dipyrrinones studied exhibit intermolecular hydrogen bonding in chloroform, as detected by 1H‐nmr, and the influence of the carboxyl group on the uv‐visible spectrum decreases with increasing chain length.

Homorubins and homoverdins

“…Some synthetic precursors were available from previous work [49]: ethyl 5-(ethoxycarbonyl)-2,4-dimethyl-1 H -pyrrole-3-propanoate ( 7 ) and the corresponding 3-butanoate ( 8 ).…”

Studies on the Structure and Function of Phytochromes as Photoreceptors Based on Synthetic Organic Chemistry

“…16,42 A variety of the methods for the synthesis of such 3,4-disubstituted pyrrolinone derivatives have been so far reported: 44,[91][92][93] the modification of the Paarl-Knorr synthesis, 94 intramolecular Horner-Emmons cyclization, 95 condensation of acetoaminoketone with cyanoacetate, 96 and reductive cyclization of the cyanohydrin derivatives of -ketoester. 97 In addition, direct structural transformation of substituted pyrroles to the corresponding pyrrolinones has been studied.…”

(m.n)-Homorubins: syntheses and structures

“…Here and in the (2.2)- and (2.3)-homorubin, the required center dipyrrole sections differed only by the length of the carboxylic acid chain: acetic vs. the propionic and butyric of earlier work [13, 14]. Thus, as shown in Scheme 4, the α-CH 3 of the known mono-pyrrole diester 11-1 [23] was converted to the α-CHO of 22 in 66% yield by oxidation using ceric ammonium nitrate [31, 32], and 22 was coupled to afford dipyrrylethene 21 in 46% yield by the McMurry coupling procedure [13, 14, 34] using Ti°. The central C=C of 21 in ethyl acetate was smoothly hydrogenated (H 2 /Pd(C)) to give a 99% yield of dipyrrylethane tetra-ester 20e , which was saponified in ethanolic NaOH to its tetra-acid 20 in 99% yield.…”

“…The target mono-acetylenes would thus be 7-n for which we envisioned introduction of the acetylene by a Sonogashira reaction [20–22] of trimethylsilyl acetylene with an α-iodopyrrole ( 9-n ). The α-iodopyrroles 10-n were prepared in four steps from simple, acyclic starting materials: diethyl oximinomalonate and the known acyl-oxo-esters 12-n [23] to afford mono-pyrrole diesters 11-n , prepared in connection with earlier synthetic work [23]. …”

“…Some synthetic precursors were prepared as in previous work: 3-pyrrolin-2-one ( 17 ) [29], ethyl 3-[2-(ethoxycarbonyl)ethyl]-4,5-dimethyl-1 H -pyrrole-2-carboxylate ( 19 ) [18], ethyl 5-carboxyethyl-2,4-dimethyl-1 H -pyrrole-3-acetate ( 11-1 ) [23], and the corresponding 3-propanoate ( 11-2 ) and 3-butanoate ( 11-3 ) [23]. …”