Catalytic Hydrogenation of Some 2-Acetamidoaldose Derivatives

In earlier work, the double bond in aldohexopyranose derivatives with the grouping C=CNAc2 was shown to be resistant to catalytic reduction. Further examples of this phenomenon are now described. Thus, compounds IV, V, and VI were found to be unaltered by hydrogen in the presence of a palladium catalyst. However, 1,4,6-tri-0-acetyl -2- (N-acetylacetamido) -2,3-dideoxy- a-D- erythro-hex-2-enopyranose (VII) and its D-threo isomer VIII undergo allylic hydrogenolysis of the C-1 acetoxy group with migration of the double bond to the C-1-C-2 position to give IX and X, respectively. The acetamido group does not inhibit the reduction of adjacent double bonds; 2-acetamido-1,4,6-tri-0-acetyl- 2,3-dideoxy-a-o-erythro-hex-2-enopyranose (XIII) and 2-acetamido- 4,6-di-0-acetyl -1-0-benzoyl-2,3-dideoxy-a-o-erythro-hex-2- -enopyranose (XV) are reduced to the same 2-acetamido-4,6-di-O- -acetyl-1,5-anhydro-2,3-dideoxy-o-arabino (or o-ribo)-hexitol (XIV) and 2-acetamido-1,4,6-tri-0-acetyl-2,3-dideoxy-~-D-arabino (or o- ribo)-hexopyranose (XX). Some mechanistic features of these reactions are pointed out. The pattern of selectivity shown in the hydrogenation is discussed and a rationalization of the observed facts is offered

Vodenjarska i močvarna vegetacija Virova u Posavini (Hrvatska)

In this work the results of phytosociological analysis of the water plant and swamp vegetation in the locality of Virovi in Slavonia (Croatia) are given. The analysis includes associations from the class Lemnetea, the order Hydrocharietalia (Hydrocharitetum morsus-ranae) and the order Utricularietalia minoris (Lemno-Utricularietum vulgaris), from the class Potametea, the order Potametalia (Ceratophylletum demersi and Nymphaeetum albo-luteae) and from the class Phragmiti-Magnocaricetea, the order Phragmitetalia (Typhetum angustifoliae).U radu se navode rezultati fitocenološke analize vegetacije vodenjara i močvara na lokalitetu Virovi u Slavoniji (Hrvatska). Analizirane su asocijacije iz razreda Lemnetea, reda Hydrocharietalia (Hydrocharitetum morsus-ranae) i reda Utricularietalia minoris (Lemno-Utricularietum vulgaris), iz razreda Potametea i reda Potametalia (Ceratophylletum demersi i Nymphaeetum albo-luteae), te iz razreda Phragmiti-Magnocaricetea i reda Phragmitetalia (Typhetum angustifoliae)

Catalytic Hydrogenation of Some 2-Acetamidoaldose Derivatives

In earlier work, the double bond in aldohexopyranose derivatives with the grouping C=CNAc2 was shown to be resistant to catalytic reduction. Further examples of this phenomenon are now described. Thus, compounds IV, V, and VI were found to be unaltered by hydrogen in the presence of a palladium catalyst. However, 1,4,6-tri-0-acetyl -2- (N-acetylacetamido) -2,3-dideoxy- a-D- erythro-hex-2-enopyranose (VII) and its D-threo isomer VIII undergo allylic hydrogenolysis of the C-1 acetoxy group with migration of the double bond to the C-1-C-2 position to give IX and X, respectively. The acetamido group does not inhibit the reduction of adjacent double bonds; 2-acetamido-1,4,6-tri-0-acetyl- 2,3-dideoxy-a-o-erythro-hex-2-enopyranose (XIII) and 2-acetamido- 4,6-di-0-acetyl -1-0-benzoyl-2,3-dideoxy-a-o-erythro-hex-2- -enopyranose (XV) are reduced to the same 2-acetamido-4,6-di-O- -acetyl-1,5-anhydro-2,3-dideoxy-o-arabino (or o-ribo)-hexitol (XIV) and 2-acetamido-1,4,6-tri-0-acetyl-2,3-dideoxy-~-D-arabino (or o- ribo)-hexopyranose (XX). Some mechanistic features of these reactions are pointed out. The pattern of selectivity shown in the hydrogenation is discussed and a rationalization of the observed facts is offered

Estimates for the Gauss four-point formula for functions with low degree of smoothness

AbstractThe aim of this work is to derive the Gauss four-point quadrature formula using Euler-type identities. The advantage of this approach is that it enables us to obtain estimates of the error for functions with low degree of smoothness and also to produce quadrature formulae which contain values of derivatives at the end points of the interval