Thermodynamic properties of hexacosane

The heat capacity of a purified sample of hexacosane, n-C₂₆H₅₄, has been measured from 13 to 358 K. The enthalpies of transition near 325.5 K and fusion at 329.25 K, and the purity of the sample have been determined; the accuracy of the results is influenced by the closeness in temperature, and overlap, of the crystal-to-crystal and crystal-to-liquid phase transitions. Thermodynamic properties have been calculated from the heat capacities and enthalpies.     

The Tricyclooctanone Approach to the Total Synthesis of Steroids. The Cyclization of the A-CD Unit

The first steps of a novel approach to the total synthesis of 9, 11-dehydroestrone via tricyclo[3.3.0.0^2,8]octan-3-one (2) are described. One route involves a tandem-type transformation of the key intermediate 3 (A-CD unit) consisting of cyclopropane cleavage and ring B closure to afford C, 18-bisnor-13 α, 17 α-estradiol derivatives. E.g. the 3-methoxy-9 ζ-hydroxy-17 α-methanesulfonyloxy derivative (-)- 6 has been synthesized in 8 steps and 10% overall yield from 1,3-cyclohexadiene. As an alternative, the A-CD type intermediate 4b has been prepared and could be used for a ring C enlargement prior to cyclization.     

Biogenetically inspired approach to the Strychnos alkaloids. Concise syntheses of (+/-)-akuammicine and (+/-)-strychnine

A linear synthesis of the indole alkaloid (+/-)-akuammicine (2) was completed by a novel sequence of reactions requiring only 10 steps from commercially available starting materials. The approach features a tandem vinylogous Mannich addition and an intramolecular hetero Diels-Alder reaction to rapidly assemble the pentacyclic heteroyohimboid derivative 8 from the readily available hydrocarboline 6. Oxidation of the E ring of 8 gave the lactone 9 that was converted into deformylgeissoschizine (11). The subsequent elaboration of 11 into 2 was effected by a biomimetically patterned transformation that involved sequential oxidation and base-induced skeletal reorganization. A variation of these tactics was then applied to the synthesis of the C(18) hydroxylated akuammicine derivative 36. Because 36 had previously been converted into strychnine (1) in four steps, its preparation constitutes a concise, formal synthesis of this complex alkaloid.     

Synthesis of Oncinotin-11-one,a Macrocyclic Polyamine Alkaloid from Oncinotis tenuiloba

This paper presents a short synthesis of oncinotin-11-one ( 11 ), a minor alkaloid of Oncinotis tenuiloba (Apocynaceae). Based on a disconnection approach, the spermidine portion of the key intermediate 6 was constructed consecutively by simple N-alkylations starting from ethyl piperidine-2-carboxylate ( 1 ). Treatment of 6 with in situ lithiated 2-[(10-bromodecyl)oxy]tetrahydropyran resulted in the formation of the keto moiety under simultanous deprotection of the lactam N-atom to give the amino ketone 7 in 71% yield. Cleavage of the tetrahydro-2H-pyran-2-yl(Thp) portion and Jones oxidation of the resulting alcohol 8 gave the amino acid 9 which was cyclized. Final N-debenzylation of 10 provided the natural alkaloid 11 . Only two protective groups were needed in this synthesis. The reaction of N-alkyl-lactams with organometallic reagents is discussed.     

Boundary conditions and mode jumping in the buckling of a rectangular plate

We show that mode jumping in the buckling of a rectangular plate may be explained by a secondary bifurcation — as suggested by Bauer et al. [1] — when clamped boundary conditions on the vertical displacement function are assumed. In our analysis we use the singularity theory of mappings in the presence of a symmetry group to analyse the bifurcation equation obtained by the Lyapunov-Schmidt reduction applied to the Von Kármán equations. Noteworthy is the fact that this explanation fails when the assumed boundary conditions are simply supported.Mode jumping in the presence of clamped boundary conditions was observed experimentally by Stein [9]; simply supported boundary conditions are frequently studied but are difficult — if not impossible — to realize physically. Thus, it is important to observe that the qualitative post-buckling behavior depends on which idealization for the boundary conditions one chooses.Research sponsored in part by the U.S. Army Contract DAAG29-75-C-0024 and the N.S.F. Grant MCS77-04148Research partially supported by the N.S.F. Grant MCS77-03685 and the Research Foundation of C.U.N.Y.     

Production of lepton pairs in processes with hadronic jets

We propose a model for the production of extra (additional) lepton pairs in deep inelastic lepton-hadron scattering, e⁺e^– annihilation and large p_T processes. Extra lepton pairs are supposed to be originated by annihilations of quarks and antiquarks created during the space-time evolution of quark initiated jets. This mechanism yields predominantly dileptons with rather low masses. Predictions following from the model are compared with the recent data on trimuon production in neutrino-nucleon interactions. It is also suggested that internal hard processes can lead to dileptons with both small and large masses. The latter mechanism has rather small cross section but it is particularly interesting from the point of view of the simple quark-parton model.Dedicated to Academician Václav Votruba on the occasion of his seventieth birthday.     

On the Gauss type quadrature with parametric weight function

Acta Mathematica Hungarica -