The crystal structure of an efficient Diels-Alder antibody catalyst at 1.9 angstrom resolution reveals almost perfect shape complementarity with its transition state analog. Comparison with highly related progesterone and Diels-Alderase antibodies that arose from the same primordial germ line template shows the relatively subtle mutational steps that were able to evolve both structural complementarity and catalytic efficiency.

The photochemically reversible trans-cis isomerisation of (E)-hex-3-ene-1,5-diynes (1,2-diethynylethenes, DEEs) and 3,4-diethynylhex-3-ene-1,5-diynes (tetraethynylethenes, TEEs) substituted with electrondonating (p-dialkylaminophenyl) and/or electron-accepting (p-nitrophenyl) groups has been examined. The type and degree of donor/acceptor (D/A) functionalisation has been found to drastically affect the partial quantum yields of isomerisation t→c and c→t . Total quantum yields in n-hexane vary from total ‫؍‬ 0.72 for a bis-acceptor substituted TEE to total ‫؍‬ 0.015 for a four-fold, bis-donor, bis-acceptor substituted TEE derivative. A strong relationship between total and solvent polarity as well as a strong dependence of t→c and c→t on the wavelength of excitation exc has been observed. The temperature dependence of the photoisomerisation has been investigated for a bis-acceptor-substituted DEE and shows no changes in total over the temperature range 6.5-65 ЊC. None of the compounds studied undergoes thermal isomerisation at 27 ЊC in n-hexane. Further analysis of these compounds by theoretical investigations at the semiempirical level of theory reveals a significant reduction of the bond order of the central olefinic double bond in the D-D, D-A and A-A TEEs upon electronic excitation, thus ultimately facilitating photoisomerisation.

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Radical addition of cysteamine to anomeric allyl glycosides of Kdo 5-phosphates 1 and 4 afforded good yields of the corresponding 3-(2-aminoethylthio)propyl glycosides. Similar reactions with the α-allyl glycoside of Kdo 4-phosphate 7 led to substantial formation of the dephosphorylated product 10 through intramolecular hydrolysis of the 4-O-phosphomonoester by the terminal amino function of the spacer group. Similar side reactions occurred upon deblocking of the 4- O-phosphorylated 6-aminohexyl-α-glycoside lactone derivative 18. Allyl glycosides of 4'- O- and 5'- O-phosphorylated Kd↬ (2 6)-glucosamine derivatives were prepared in good yields via phosphorylation using the amidite procedure. The 4'-phosphate moiety was introduced following intramolecular protection of the 5'-OH group as a lactone. Subsequent deprotection gave the allyl glycosides 25 and 33 which were transformed into the corresponding stable spacer derivatives 26 and 34 by coupling with cysteamine. The ligands were activated with thiophosgene and reacted with bovine serum albumin to give the neoglycoconjugates 3, 6, 27 and 35 to be used in immunochemical studies of monoclonal antibodies directed against Haemophilus influenzae Re-mutant and related lipopolysaccharides.

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