STUDY OF THE MECHANISM OF 12C（d,d）12C AND 12C（d,p）13C* REACTIONS

A formalism for studying the interference between the direct reaction and the compound resonance processes is presented by the S-matrix theory; The mechanism of ¹²C（d, d） ¹²C, ¹²C（d, p₁） ¹³C* and ¹²C（d, p₂） ¹³C* reactions in the energy range E_d=1.63 MeV to 2.05 MeV is analysed.Te results show that: the interference between these two processes exists; and the quantitative relation between them is given. While the parameters of direct reactions and compound resonance processes, particularly for four resonance states with E_d=1.726, 1.767, 1.792 and 1.86 MeV are determined.     

The amide group in N-acetylglucosamine glycosyl acceptors affects glycosylation outcome

Glycosylation of a disaccharide containing N-acetylglucosamine with rhamnosyl and mannosyl trichloracetimidates under triethysilyl triflate catalysis led to the competitive formation of glycosyl imidates. While the rhamnosyl imidate could be rearranged to the thermodynamically favored trisaccharide, the mannosyl analogue was resistant to rearrangement. Glycosylation with perbenzylated thiorhamnosides activated with methyl triflate (MeOTf) gave the trisaccharide as well as the methyl imidate trisaccharide. The less reactive alpha-thioethyl donor led to a higher relative amount of methyl imidate trisaccharide to trisaccharide than the more reactive beta-thioglycoside. When using a more reactive thioethyl fucoside only the trisaccharide was obtained. Interestingly, the acceptor treated with MeOTf gave the N-methyl imidate that could be easily rhamnosylated and subsequently converted to the N-acetamido trisaccharide. This strategy to glycosylate O-4 of N-acetylglucosamine is under further investigation. Alternatively, bis-N-acetylation of the glucosamine prevented the formation of imidates and allowed the efficient synthesis of two Lewis A trisaccharide analogues.     

Convenient temporary methyl imidate protection of N-acetylglucosamine and glycosylation at O-4

This paper expands on the scope and utility of the temporary conversion of N-acetyl groups to alkyl imidates when attempting to glycosylate at O-4 of N-acetylglucosamine acceptors. The optimized synthesis of alkyl imidate protected glucosamine acceptors at position 4 and carrying various protecting groups at O-3 is described. These imidates were prepared immediately prior to glycosylation by treating the 4-OH acceptors with 0.5 M MeOTf to obtain the corresponding methyl imidates still carrying a free 4-OH group. When preparing these imidates in diethyl ether as the reaction solvent, we observed the unexpected formation of ethyl imidates in addition to the desired methyl imidates. While the 3-O-allyl acceptors were too unstable to be useful in glycosylation reactions, the 3-O-acylated methyl and ethyl imidates of glucosamine were shown to behave well during the glycosylation of the 4-OH with a variety of reaction conditions and various glycosyl donors. Glycosylation of these acceptors was successfully carried out with perbenzylated beta-thioethyl rhamnopyranoside under MeOTf promotion, while activation of this donor under NIS/TMSOTf or NIS/TfOH proved less successful. In contrast, activation of the less reactive perbenzylated alpha-thioethyl and peracetylated beta-thioethyl rhamnopyranosides with NIS/TfOH led to successful glycosylations of the 4-OH. Activation of a peracetylated rhamnosyl trichloroacetimidate by TMSOTf at low temperature also gave a high yield of glycosylation. We also report one-pot glycosylation reactions via alkyl imidate protected acceptor intermediates. In all cases the alkyl imidate products were readily converted to their corresponding N-acetyl derivatives under mild conditions.     

Selective protection of 2-azido-lactose and in situ Ferrier rearrangement during glycosylation: synthesis of a dimeric Lewis X fragment

In our efforts to design new anti-cancer vaccines based on the tumor associated carbohydrate antigen dimeric Lex, we have synthesized the fragment GlcNAc-beta-(1-->3)-Gal-beta-(1-->4)-GlcNAc-beta-(1-->O)-Me. Although it is notoriously difficult to chemically protect the primary OH groups in beta-lactoside derivatives, a 6,6'-disilylated intermediate was prepared in 82% yield. It was converted to a glycosyl acceptor free at O-3' that was glycosylated with a 2-deoxy-2-phthalimido trichloroacetimidate glucosyl donor. This glycosylation required large amounts of TMSOTf to proceed. Such conditions led to the formation of a Ferrier rearrangement glycosylation product. Despite these hurdles, the desired trisaccharide was isolated in 53% yield and easily deprotected in four steps.     

Combining rule for interaction energies of the (CO)2, (N2)2 and CO-N2 complexes

The relationship between interaction energies of the most stable structures of the (CO)₂, (N₂)₂ and CO-N₂ complexes is investigated using the supermolecule CCSD(T) and MP4 methods and aug-cc-pVXZ (X = D,T,Q) basis sets extended by a set of midbond functions centred in the middle of the intermolecular bond. A simple combining rule for interaction energies of this triad of clusters is proposed.     

Glycosylation of N-acetylglucosamine: imidate formation and unexpected conformation

[structure: see text] Rhamnosylation in mild conditions of a disaccharide containing N-acetylglucosamine afforded the imidate 6 while at higher temperature and concentration of promoter trisaccharide 7 was isolated. The kinetic imidate 6 was independently rearranged in 50% yield to the thermodynamic trisaccharide 7. Comparative NMR studies of 7 in CDCl(3) and DMSO-d(6) suggest the formation of a nonchair conformation in CDCl(3). The structure of 7 was confirmed through the independent synthesis of the N-acetylacetamido trisaccharide 11.     

ADSORPTION DYNAMICS OF MACROPOROUS POLYMERIC ADSORBENT Ⅱ. The Studies on the Film Diffusion Mass-Transfer Process

1 INTRODUCTIONAt present time, most of the studies for the adsorption dynamics of macroporous adsorbent,.especially for the film diffusion mass-transfer process, were based on the conclusions for theBoyd ion-exchange dynamics equationl'l. The structure of gel-type ion-exchange resin andmacroporous polystyrene resin is different. Because of having the hydrophilic group, both of theirmer and outer of the ion-exchange resin can swell to the reticulation struCture in the aqueous.Based on the…