Evaluating the use of chiral anthracene templates to access pyroglutamic acids

An approach for the asymmetric synthesis of pyroglutamic acid derivatives is described based on an anthracene chiral auxiliary. The introduction of a furan ring as a masked carboxylic acid moiety proceeded with excellent levels of diastereo-selectivity, followed by conversion into a carboxylate ester. The ensuing retro-Diels–Alder procedure using flash vacuum pyrolysis (FVP) followed by reduction gave pyroglutamate esters in good yield but poor enantioselectivity, the latter of which was found to be dependant on the electronic nature of the N-protecting group.     

A simulation-based approach to the study of coefficient of variation of Gompertz distribution under progressive first-failure censoring

In applied statistics, the coefficient of variation is widely used. However, inference concerning the coefficient of variation of non-normal distributions are rarely reported. In this article, a simulation-based Bayesian approach is adopted to estimate the coefficient of variation (CV) under progressive first-failure censored data from Gompertz distribution. The sampling schemes such as, first-failure censoring, progressive type II censoring, type II censoring and complete sample can be obtained as special cases of the progressive first-failure censored scheme. The simulation-based approach will give us a point estimate as well as the empirical sampling distribution of CV. The joint prior density as a product of conditional gamma density and inverted gamma density for the unknown Gompertz parameters are considered. In addition, the results of maximum likelihood and parametric bootstrap techniques are also proposed. An analysis of a real life data set is presented for illustrative purposes. Results from simulation studies assessing the performance of our proposed method are included.     

Interfacial synthesis and properties of L-lysine-derived optically active poly(ester-imide)s

L-Lysine hydrochloride was transformed to ethyl L-lysine dihydrochloride.This salt was reacted with trimellitic anhydride to yield the corresponding diacid（1）.Intertacial polycondensation results novel poly（ester-imide）s(PEI_a-i).These polymers have inherent viscosities in the range of 0.23-0.47 dl g^-1,display optical activity,and are readily soluble in polar aprotic solvents.They start to decompose(T_10%) above 350℃and display glass-transition temperatures at 100.42-172.81℃.All of the above polymers were fully characterized by UV,FT-IR and ¹H NMR spectroscopy,elemental analysis,TGA,DSC,inherent viscosity measurement and specific rotation.     

The order bidual of <Emphasis Type="Italic">f</Emphasis> -algebras revisited

It is shown that the order bidual X ^~~ of an Archimedean semiprime f -algebra X has a unit element for the Arens multiplication if and only if every positive linear functional on X extends to a positive linear functional on the f -algebra Orth (X) of all orthomorphisms on X.     

Corrigendum to: Representation Theorems for d-Multiplications on Archimedean f-Rings

In this note we intend to correct a misprint in our earlier article on representation of d-multiplications on Archimedean f-rings.     

Variation of <Superscript>231</Superscript>Pa, <Superscript>230</Superscript>Th and <Superscript>231</Superscript>Pa<Subscript>ex</Subscript>/<Superscript>230</Superscript>Th<Subscript>ex</Subscript> in surface sediments of the Sabah–Sarawak coastal waters

Protactinium and thorium activities were measured in eight surface sediment taken in 2004 to determine effectiveness scavenging of ²³¹Pa at Sabah–Sarawak coastal waters. The result found that activity ratios of ²³¹Pa_ex/²³⁰Th_ex were ranged from 0.07 to 0.13 at all sampling stations. The high ²³¹Pa_ex/²³⁰Th_ex activity ratio than the production ratio of 0.093 in seawater at station SR 01, SR 02, SR 04, SB 02 and SB 05, revealed that ²³¹Pa is effectively removed from the water column into the sediment in comparison with ²³⁰Th at those stations. Low percentage of ²³⁰Th_ex (90–95%) in comparison with ²³¹Pa_ex at all stations can be attributed to less efficiently scavenged of ²³⁰Th onto particles prior deposited at the marine sediment bed.     

Dimorphamides A – C,New Polyphenolic Amides from Atriplex dimorphostagia

Dimorphamides A–C ( 1 – 3 , resp.), three new polyphenolic amides, have been isolated from the BuOH‐soluble fraction of the whole plant of Atriplex dimorphostagia, along with two known compounds, thymidine and N‐[(E)‐feruloyl]tyramine. Their structures have been determined on the basis of spectral studies.