Quasi-Symmetric Designs with Good Blocks and Intersection Number One

We show that a quasi-symmetric design with intersection numbers 1 and y > 1 and a good block belongs to one of three types: (a) it has the same parameters as PG ₂(4, q), the design of points and planes in projective 4-space; (b) it is the 2-(23, 7, 21) Witt design; (c) its parameters may be written v = 1 + (( – 1) + 1)(y – 1) and k = 1 + (y – 1), where is an integer and > y 5, and the design induced on a good block is a 2-(k, y, 1) design. No design of type (c) is known; moreover, for large ranges of the parameters, it cannot exist for arithmetic reasons concerning the parameters. We show also that PG ₂(4, q) is the only design of type (a) in which all blocks are good.     

Preparation and properties of triorganostannylmethyl 2,3:5,6-di-O-isopropylidene-α-D-mannofuranosides; pesticidal and fungicidal activities of triphenylstannyl-carbohydrate derivates

The synthesis of trioganostannylmethyl 2,3:5,6-di-O-isopropylidene-α-D-mannofuranoside (compound 3, R*OCH₂SnR₂R′:R?R′?Me or Ph) from D-mannose is reported. The compound 3 (R?R′?Ph) is transmetallated by PhLi to compound 5, R*OCH₂Li, Which can be trapped by HgCl₂ [as (R*OCH₂)₂Hg] and by ketones, R³COMe [as compound 7, R*OCH₂CR³MeOH]. Two stereoisomers of this compound (7a, R³?Ph) were formed in a ratio of 40:60, indicating some asymmetric induction, arising from the chiral R* moiety. Reactions of compound 3, (R?R′?Ph), with I₂, HO₂CCF₃ and Cl₂PtCOD result in Ph–Sn bond cleavage and formation of compound 3 with R?Ph; R′?I, OCOCF₃ and Cl respectively. Reactions of compound 3 (R?R′?Me) with electrophiles can lead to cleavage of either of both types of C–Sn bonds present (e.g. by I₂, Br₂, Cl₂PtCOD or SnCl₄) or to attack at the C₅–C₆ protecting group with release of acetone (e.g. by CF₃CO₂H, SO₂ or CH₃COCl). Pesticidal and fungicidal activities of compound 3(R?R′?Ph) as well as of 1,2:5,6-di-O-isopropylidene-3-O(triphenylstannylmethyl)-α-D-glucofuranose (compound 2, R?Ph) and methyl 4, 6-O-benzylidene-2-deoxy-2-triphenylstannyl-α-D-altropyranoside (compound 1, R?Ph) are reported.     

Synthesis of backbone modified cyclic peptides bearing dipicolylamino sidearms

Three analogues of the Lissoclinum class of cyclic peptides, bearing dipicolylamino functionalised side chains, have been synthesised using a stepwise approach followed by macrocyclisation. Attempts to incorporate dipicolylamino functionalised side chains prior to peptide synthesis resulted in epimerisation, but this was overcome by functionalising the ornithine side chains with dipicolylamino groups after the macrocyclisation reaction.     

Combined 1H NMR and DFT study of the solvent effects on the iron pentacarbonyl‐catalyzed photo‐assisted isomerization of allyl alcohol

The relative rates of iron pentacarbonyl‐catalyzed photo‐induced isomerization of allyl alcohol to propanal in various solvents have been measured using ¹H NMR spectroscopy. The reactions were run in linear and cyclic alkanes, alcohols, and amines in order to investigate solvent effects on the isomerization mechanism upon ultraviolet irradiation. The isomerization was efficient in nonane, hexane, cyclohexane, and benzene. The isomerization was very slow or completely suppressed in ethanol, propanol, isopropanol, triethylamine, and pyridine. Density functional theory calculations predicted thermodynamically favorable (ΔG^o < 0) formation of Fe(CO)₄–solvent compounds in the suppressing alcohol/amine solvents and unfavorable (ΔG^o > 0) formation in the hydrocarbon solvents. The strong solvent ligation likely prevents formation of Fe(CO)₃●(η²‐alkene) necessary for isomerization. Copyright © 2013 John Wiley & Sons, Ltd.