A facile construction of the typical framework of narcissus alkaloids has been realized by virtue of the development of a practical route involving stereocontrolled epoxide formation and SnCl(4)-catalyzed arene-epoxide coupling. To achieve this goal, it proved to be necessary to devise a strategy that would enable chemical transformations to install an epoxy moiety in a congested environment. The successful preparation of a hindered epoxide from O-isopropylidene-protected 4-aminocyclohexenol required three steps consisting principally of controlled bromohydration and base-promoted closure and N-alkylation. It was found that a catalytic amount of SnCl(4) not only maintained the catalytic cycle but also effected clean arylation to form a fused BC ring system. Several tactics that ultimately proved to be unsatisfactory are also discussed in an effort to set important boundary limits on arene-epoxide coupling. The requisite enantiopure 4-aminocyclohexenol was available via an asymmetric cycloaddition of diene to camphor-based chloronitroso. The total synthesis of (+)-narciclasine was realized in nine steps with an overall yield of 19%.

This work for the first time reports X-ray crystals of the two mononuclear mercury(II) porphyrin complexes, i.e., a four-coordinate complex Hg(p-CN)4tpp (1) and a five-coordinate complex Hg(N-Me-tpp)Cl (2). Compound 1 is distorted square planar, whereas compound 2 is trigonal bipyramidal distorted square-based pyramid in which the apical site is occupied by a N(1) atom.

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The crystal structures of N-benzamido-meso-tetraphenylporphyrin (NHCOC(6)H(5)-Htpp; 1), (N-benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II) [Zn(N-NCOC(6)H(5)-tpp)(MeOH); 2(MeOH)], and (acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCOC(6)H(5)-tpp)(OAc); 3] were established. The coordination sphere around Zn(2+) ion in 2(MeOH) is a distorted trigonal bipyramid with N(2), N(5), and O(2) lying in the equatorial plane, whereas, for Cd(2+) ion in 3, it is a sitting-atop derivative with a distorted trigonal bipyramidal geometry in which the apical site is occupied by atoms N(2) and O(2). Cd in 3 acquires five-coordination with five strong bonds [Cd(1)-N(1) = 2.319(5) A, Cd(1)-N(2) = 2.252(5) A, Cd(1)-N(3) = 2.332(5) A, Cd(1)-O(2) = 2.292(5) A, and Cd(1)-O(3) = 2.317(5) A] and with one secondary intramolecular interaction [Cd(1)...N(4)]. The porphyrin ring in these two complexes is distorted to a large extent. The plane of the three pyrrole nitrogen atoms [i.e., N(1)-N(3)] strongly bonded to Zn(2+) in 2(MeOH) and to Cd(2+) in 3 is adopted as a reference plane 3N. For the Zn(2+) complex, the pyrrole nitrogen bonded to the benzamido (BA) ligand lies in a plane with a dihedral angle of 33.8 degrees with respect to the 3N plane, but for the Cd(2+) complex, this dihedral angle is found to be 31.4 degrees. In the former complex, Zn(2+) and N(5) are located on the different side at -0.08 and 1.39 A from its 3N plane, and in the latter one, Cd(2+) and N(5) are also located on the different side at 1.08 and -1.51 A from its 3N plane. VT NMR ((1)H and (13)C) studies of 3 show that the acetate acts as a bidentate ligand and the OAc(-) exchange does not occur in CD(2)Cl(2). Moreover, the NH proton [i.e., H(5)] of 3 in CD(2)Cl(2) is observed as a sharp singlet at delta = -1.13 ppm with Delta nu(1/2) = 4 Hz at 20 degrees C indicating that the intermolecular proton exchange between water and NH proton is rapid.