Naslov
Structure of 4, 5-Ethylenedioxy-4, 5-dihydro-1, 3-dimethyluric Acid

Autori
Luić, M. ; Modrić, N. ; Poje, M. ; Vicković, I.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
XXII. konferencija jugoslavenskog centra za kristalografiju

Mjesto i datum
Mostar, Bosna i Hercegovina, 1987

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
chemical models; uric acid glycol; intermediate; oxidative breakdown; regiospecific; stereoelectronic control; glycol ethers

Sažetak
In the course of study of the relationship between the molecular conformation and reactivity of appropriate chemical models it was shown that uric acid glycol, the key intermediate in oxidative breakdown of purines, can exist in two distinct ring-twisted conformations of the cis-fused bicyclic system. Regiospecific ring opening requires that the pi-type electron pair on one ureide N atom lies parallel and one non-bonded electron pair on the O atom antiperiplanar to the leaving N atom of the tetrahedral ester aminal array at C(4). In order to ascertain the stereoelectronic control in the cleavage of uric acid glycol, we have constructed a conformationally rigid propellane-type ether, 4, 5-ethylenedioxy-4, 5-dihydro-1, 3-dimethyluric acid, in whivh non-bonded electrons on C(4) are oriented in such a way that the cleavage of the ester aminal function cannot occur with the help of electronic control. As a result of this conformationally rigid arrangement the O atom of the ester aminal function becomes locked into a configuration where cleavage of the C(4)-N(9) bond is no longer stereoelectronically allowed since the O(4) electron pair is no longer antiperiplanar to the N(9) atom. This derivative must, therefore, be unreactive and, indeed, it was completely stable under mild acidic conditions that are normally used for the hydrolysis of other uric glycol ethers. Crystal data: C9N4O5H12, M=256.22, orthorombic, space group Pna21, a=15.187(5), b=12.883(3), c=11.468(3)Angstrom, V=2244(1)Angstrom3, Z=8, Dc=1.517 Mgm-3, F(000)=1072, mi(CuKalpha)=10.92 cm-1, lambda=1.54178Angstrom. The integrated intensities of 1865 independent reflections were collected on an Philips PW-1100 diffractometer. Lorentz and polarization corrections were applied and unobserved reflections have been inserted(INSERT program). We tryed to solve the crystal structure by means of direct methods. MULTAN failed, but SIR reveiled 34 out of 36 non-hydrogen atoms in two independent molecules. The anisotropic refinement of all non-hydrogen atoms yielded a present R=0.056 in the SHELX 76 program. The CSU program have been used for geometry analysis of the structure, whose further elucidation is in progress.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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