Ethyl 2,3-dideoxy-a-D-erythro-hex-2;enopyranosde (9a) an accessible and highly crystalline substance is selectively oxidized at the allylic position to ethyl 2,3-dideoxy-a-~-glycero-hex-2-enopyranosid-4-ulose (10a) in 80% yield. This hydroxyketone can be benzoylated, acetylated, and tosylated, and the resulting esters are all highly crystalline, as is the parent ketone. 3,4-Di-0-acetyl-D-xylal reacts with ethanol under boron trifluoride catalysis to give the anomeric mixture of ethyl 4-0-acetyl 2,3-dideoxy-D-glycero-pent-2-enopyranosides which may be separated after deacetylation. The deacetylated a-D anomer (14a) is readily oxidized by manganese dioxide to give an ethyl 2,3-dideoxy pent-2-enopyranosid-4-ulose (6-ethoxy-2,6-dihydropyran-3-one) (12); however, the corresponding !3-D (14!3) anomer resists oxidation. All of these ketones display a diagnostic nuclear magnetic resonance pattern consisting of clean doublets for H-l and -3, and a doublet of doublets for H-2. Reduction of 10a with lithium aluminum hydride gives back the parent D-erytkro alcohol exclusively, and catalytic hydrogenation saturates the olefinic double bond. These a,B-unsaturated ketones (10) in the hexose series are all levorotatory although their parent D-erythro alcohols (9) are strongly dextrorotatory; the saturated ketones derived from them are also strongly dextrorotatory. The epimeric D-threo alcohols which should also be oxidizable to 10 are however strongly levorotatory.

Spectroscopically and chemically well-defined complexes have been observed in the NinA zeolites.1 The Ni11 ions in a trigonal, almost planar coordination in the zeolitic network combine with various molecules(2) These assignments are meaningful since it has been shown (R. Polak and K. Klier, ibid., in press) that the low symmetry field behaves as a strong ligand field in all relevant cases.

No abstract

the latter to the corresponding alcohol (11; R = CH2:CCl*CH2) proceeded uneventfully but the alcohol did not react with Lewis acids by ring closure onto the chloropropenyl group (cf. ref. lo), instead it underwent ( Y) (Yl1 simple dehydration to (V; R = CH2:CC1*CH2). 2-Dimethylaminoethyl chloride only reacted with the amino-ketone (I; R1 = R2 = H) in the presence of sodamide [giving (I;

When alcohol solutions of N-diphenylmethylenebenzylamine (Id) are irradiated in the presence of benzophenone with light of intensity -200 W there is predominant formation of the ~r~~syttlnletrical dihydrophotodimer (4) and no symmetrical dimers are detected. The dihydromonomer (2d) is also produced. However, when a more intense light source (450 W) is used no dirner of any sort is formed although the dihydromonomer is still produced. The formation of the unsyninietrical dihydrodimer (4) cannot be attributed entirely to secondary reactions of the dihydromonomer (2d) since irradiation of the latter produces both symmetrical (7) and unsynimetrical (4) dihydrodimers in the ratio 1 :2.