Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• generate 16 and 17 as homochiral materials. The major diastereoisomer 16, was then subjected to iodolactonization and this resulted in a stereoisomer mixture of (3S, 5S)-12 and (3S, 5R)-13 in a ratio of 9.4:1 (Scheme 4). Interestingly iodolactonisation of 17 gave a single product (3R, 5R)-12 ([α]D = +16

• substrate. Accordingly allyl pyrrolidine 23 was treated with 2-fluoropropionyl chloride in the presence of Hünig's base and Yb(OTf)3. This generated product 24 as a single stereoisomer. Reduction of Lewis acid from 1.0 to 0.5 eq did not adversely effect the diastereoselectivity, however a stoichiometry

• lower than 0.5 eq did compromise the stereoselectivity of the reaction. An analogous reaction with 2-fluorophenylacetyl chloride generated 25, also as a single stereoisomer. Clearly the co-ordination of the Lewis acid to the ether oxygen is exerting full stereochemical control on the reaction. This is a

Synthesis and glycosidase inhibitory activity of new hexa- substituted C8-glycomimetics

• Olivia Andriuzzi,
• Christine Gravier-Pelletier,
• Gildas Bertho,
• Thierry Prangé and
• Yves Le Merrer

Beilstein J. Org. Chem. 2005, 1, No. 12, doi:10.1186/1860-5397-1-12

• presence of N-methylmorpholine oxide and tert-butanol cleanly led to the expected cis-diol 3 in 97% yield. In analogous manner, the D-manno-cyclooctene 2 gave the corresponding cis-diol 4 in 97% yield. In each case, the cis-diol 3 or 4 has been isolated as a single stereoisomer because of the C2-axis of

• and 2 the cis-epoxide 7 or 8 has been isolated as a single stereoisomer. However, all attempts to open the epoxide ring involving various nucleophiles, sodium azide, benzylamine, n-butylamine, or serinol in different experimental conditions, protic or aprotic solvent, presence or absence of a Lewis

Mixtures of monodentate P-ligands as a means to control the diastereoselectivity in Rh-catalyzed hydrogenation of chiral alkenes

• Manfred T. Reetz and
• Hongchao Guo

Beilstein J. Org. Chem. 2005, 1, No. 3, doi:10.1186/1860-5397-1-3

• even two stereogenic centers. Ligands P18, P20 and P21[32] were used in the (S)-form. In the case of the menthyl-derivative P15, a single stereoisomer was employed, although the configuration at phosphorus is unknown.[33] The menthol-derived ligand P23 having the (S)-configuration at phosphorus was