Endo-N

The carbo-Diels-Alder reaction of acrolein with butadiene (Scheme 8.1) has been the standard reaction studied by theoretical calculations in order to investigate the influence of Lewis acids on the reaction course and several papers deal with this reaction. As an extension of an ab-initio study of the carbo-Diels-Alder reaction of butadiene with acrolein [5], Houk et al. investigated the transition-state structures and the origins of selectivity of Lewis acid-catalyzed carbo-Diels-Alder reactions [6]. Four different transition-state structures were considered (Fig. 8.4). Acrolein can add either endo (N) or exo (X), in either s-cis (C) or s-trans (T), and the Lewis acid coordinates to the carbonyl in the molecular plane, either syn or anti to the alkene. 

Chemical Name (1S-(endo,endo)] -N-( [(3-hydroxy-4,7,7-trimethylbicyclo[2.2.1 ] hept-2-yl)-amino] carbonyl] -4-methylbenzenesulfonamide... 

Satoh, A., Narita, Y., Endo, N. and Nishimura, H. 1996. Constituents of Glehnia littoralis. Biosci. Biotech. Biochem. 60 152. 

Tomiyama T, Shoji A, Kataoka K, Suwa Y, Asano S, Kaneko H, Endo N. Inhibition of amyloid beta protein aggregation neurotoxicity by rifampicin. Its possible function as a hydroxyl radical scavenger. J Biol Chem 1996 271 6839-6844. 

Figure 15. Intermediates of the catalytic cycle for the two sterochemically distinct pathways, a) shows what we have termed the endo pathway, which gives rise to the R form of the product, while b) shows the exo pathway which gives rise to the S form of the product. Relative energies in kcal/mol of each of the intermediates with respect to the cis-endo n-complex (8a) are shown for styrene as the substrate and in paranthesis for 4-(dimethylamino)styrene as the substrate.

Tomiyama, T., Shoji, A., Kataoka, K., Suwa, Y., Asano, S., Kaneko, H., and Endo, N., Inhibition of amyloid beta protein aggregation and neurotoxicity by rifampicin its possible function as a hydroxyl radical scavenger, ]. Biol. Chem., 271, 6839,1996. 

The next steps of the synthesis, which formally involves a 1,2-carbonyl transposition from C(3) to C(2) and its conversion to the desired endo-N group, followed by a Mannich condensation, are outlined in Schemes 13.2.4 -13.2.6. 

A. Nakayama, K. Suzuki, T. Enoki, K. Koga, M. Endo, N. Shindo, Electronic and magnetic properties of activated carbon fibers. Bull. Chem. Soc. Jpn., 69(2) (1996) 333-339. 

Fig. 2. Projections along the endo N—N and N—P axes in c -cyclodiphosph(III)-azanes. Atomic co-ordinates were taken from the refs, in Table 2 (H-atoms omitted)...

The differences in the rates of hydrolysis of various linkage types by a particular glycosidase can be used to provide information about this aspect of structure. Jack-bean a-D-mannosidase cleaves a-(l- 2) and a-(l- 6) linkages much faster than a-(l -> 3). Oligosaccharides, obtained by endo-N-acetyl-/J-D-glucosaminidase hydrolysis of ovalbumin, were subjected to acetolysis, which selectively cleaved the a-(l - 6) bonds. A tetrasaccharide isolated after this treatment was then incubated with jack-bean o-d-... 

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