Biosynthesis of the Spermine Alkaloid Aphelandrine

Aphelandrine ( 1 ) is shown to be biosynthesized in the root cells of Aphelandra tetragona (VAHL ) NEES from labelled putrescine ( 4 ), spermidine ( 5 ), and cinnamic acid ( 3 ). Whether spermine ( 6 ) and the (p-hydroxycinnamoyl)spermidine 8 are precursors of 1 is uncertain, since the latter is hydrolysed to a large extent before incorporation, and the former is metabolized to 4 and 5 . Methionine ( 7 ) is the source of the 3-aminopropyl unit of 5 and 6 .     

Synthese von Monomorin I,einem Spurpheromon der Pharao-Ameise (Monomorium pharaonis)

Synthesis of Monomorin I, a Trail Pheromone of the Pharao Ant (Monomorium pharaonis) Katalytic hydrogenation of the 4-nitroalkanone 5 yielded the cis-pyrrolidine ester 6 (Scheme). The preparation of 5 was accomplished by ethanolysis of the nitrocyclohexanone derivative 4 . Iodination at C(α) of 6 , followed by cyclization, gave a nearly 5:6 mixture of the two C(5)-epimers 10 / 9 of octahydroindolizine. Epimerisation of the undesired 10 to 9 and subsequent transformation of the latter gave racemic monomorine I ( 1 ; 34% yield from 5 ).     

Optimal lower bounds for cubature error on the sphere

We show that the worst-case cubature error E(Q_m;H^s) of an m-point cubature rule Q_m for functions in the unit ball of the Sobolev space H^s=H^s(S²),s>1, has the lower bound , where the constant c_s is independent of Q_m and m. This lower bound result is optimal, since we have established in previous work that there exist sequences of cubature rules for which with a constant independent of n. The method of proof is constructive: given the cubature rule Q_m, we construct explicitly a ‘bad’ function f_mH^s, which is a function for which Q_mf_m=0 and . The construction uses results about packings of spherical caps on the sphere.     

High-energy γ-rays in α-accompanied spontaneous fission of 252 C f

An experiment was performed on prompt γ-ray emission in binary and α-particle accompanied spontaneous fission of ²⁵² C f using the Darmstadt-Heidelberg 4π NaI Crystal Ball spectrometer. The enhancement in γ-ray yield, denoted as the “high-energy component”, which appears between 3.5 and 8 MeV and in the region of near-symmetric fragment mass splits, was observed to be equally pronounced in both fission modes. Analyzing the fragment mass dependence of the mean γ-ray multiplicity in both fission modes clearly identifies the disintegration of equilibrated fission fragments in a narrow mass range around the double-magic ¹³²Sn as the source of these γ-rays.     

Magnetism of an Fe65Mn35 alloy in the fcc/hcp phase region

Among the three possible phase structures (bcc, fcc and hep) of iron rich Fe₁₀₀-cMn _c alloys (c _Mn <40 at%), the two closed packed structures, fcc and hep, produce poor resolved and similar Mössbauer spectra. Therefore the evaluation of spectra collected on a sample (nominalc _Mn =35 at%) with coexisting fcc and hep phases only was possible with the help of the Afans’ev/Tsymbal method of “Mössbauer lines sharpening” introduced recently/1,2,3/. A comparison of the hyperfine field vs. temperature with an FeNi-Invar alloy (c _Ni =35 at%) shows a surprising similarity.     

Lacton-Bildung durch ringerweiternde Fragmentierung von Epoxycyclodecanon-Derivaten

Lactones from Epoxycyclodecanone Derivatives by Ring Enlargement Involving Fragmentation Reactions A stereospecific ring-enlargement reaction of alkyl esters of 2,3-epoxy-1-(3-hydroxypropyl)-10-oxocyclo-decanecarboxylic-acid derivatives is described, involving Grob fragmentation of in situ formed hemiacetals. The assignment of the relative configuration of the starting materials was accomplished on the basis of ¹H-NMR data. The rearrangement of the epoxides 9 and 10 (with cis-orientation of the ester group and the epoxide ring, Scheme 1) gives the lactone 15 as the single and as the major product, respectively, with (Z)-configuration of the newly formed C?C bond. A concerted reaction mechanism is assumed. The formation of a small amount of 12 from 10 is probably due to a competitive two-step carbanion pathway. The reaction of the diastereoisomers 7 and 8 leads to the lactones 11 and 12 , respectively, as the only ring-enlargement products (Scheme 1), with (E)-configuration of the newly formed C?C bond. On the basis of our results, we cannot distinguish in this case between a concerted and a two-step carbanion mechanism. This type of reaction takes place only in the presence of an ester group; no ring enlargement was detected in case of compound 20 (Scheme 3), which is the de(alkoxycarbonyl) derivative of 9 . The eliminative opening of the epoxide ring in the epoxylactone 17 affords 11 as the single product (Scheme 2). A carbanion mechanism was assumed for this reaction.     

Deconvolving a Density from Partially Contaminated Observations

We consider the problem of estimating a continuous bounded probability density function when independent data X₁, ..., X_n from the density are partially contaminated by measurement error. In particular, the observations Y₁, ..., Y_n are such that P(Y_j = X_j) = p and P(Y_j = X_j + ε_j) = 1 − p, where the errors ε_j are independent (of each other and of the X_j) and identically distributed from a known distribution. When p = 0 it is well known that deconvolution via kernel density estimators suffers from notoriously slow rates of convergence. For normally distributed ε_j the best possible rates are of logarithmic order pointwise and in mean square error. In this paper we demonstrate that for merely partially(0 < p <1) contaminated observations (where of course it is unknown which observations are contaminated and which are not) under mild conditions almost sure rates of order O(((log h⁻¹)/nh)^1/2) with h = h(n) = const(log n/n)^1/5 are achieved for convergence in L_∞-norm. This is equal to the optimal rate available in ordinary density estimation from direct uncontaminated observations (p = 1). A corresponding result is obtained for the mean integrated squared error.     

Zur Bestimmung des Kobalts als Co3O4

Ohne Zusammenfassung