No abstract

Malignant and trophoblastic cells share the capacity to migrate and invade surrounding tissues; however, trophoblast invasion during implantation is tightly regulated, whereas that associated with tumour progression is not. It is likely that similar mechanisms underlie the dynamic regulation of cell invasion and migration in both cases, and that these are based on epigenetic processes. This hypothesis is supported by recent results demonstrating that expression of the intercellular adhesion molecule E-cadherin, deregulation of which is associated with increased cell motility and invasive potential in cancer, is under epigenetic control in trophoblast cell lines. Further elucidation of the epigenetic pathways shared by trophoblasts and malignant cells is likely to lead to the identification of common diagnostic approaches for the early identification both of cancer and pathological pregnancies involving aberrant trophoblast invasion.

No abstract

Reversible formation of carbon–carbon bonds under physiological conditions by enzyme catalysis allows the generation and in situ screening of a dynamic mixture of biologically significant compounds. Generation of the dynamic library by incubation of the three sugars 1 a–c with two equivalents of sodium pyruvate in the presence of N‐acetylneuraminic acid aldolase and wheat germ agglutinin resulted in amplification of sialic acid 1 a (see scheme).

The reaction of (E )-1-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)-3-(trimethylsiloxy)buta-1,3-diene 1 and maleic anhydride gives cycloadduct 10 and ketone 12. Reduction of ketone 13, formed by acidic hydrolysis of silyl enol ether 10, with sodium cyanoborohydride in acetic acid gives an 83 : 17 mixture of the γand δ-lactone 14 and 15. γ-Lactone 14 is transformed into the aminomonocarba-disaccharide, 4-acetamido-2,4-dideoxy-3-O-(β--glucopyranosyl)-5a-carba-β--lyxo-hexopyranose 7, using a five-step procedure involving the Curtius rearrangement of acyl azide 16. A similar sequence using γ-lactone 21, prepared from ketone 12, gives the protected aminomonocarbadisaccharide, 4-acetamido-1,6-di-O-acetyl-2,4-dideoxy-3-O-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyl)-5a-carbaβ--lyxo-hexopyranose 8.Reaction of cycloadduct 10 with dimethyldioxirane gives acyloin 26. Acetylation under acidic conditions followed by reduction with sodium cyanoborohydride in acetic acid gives a 75 : 25 mixture of the γand δ-lactone 28 and 29. Using a sequence similar to that employed for the preparation of compounds 7 and 8, γ-lactone 28 is converted into the fully substituted aminomonocarba-disaccharide, 4-acetamido-1,2,6-tri-O-acetyl-4-deoxy-3-O-(2Ј,3Ј,4Ј,6Ј-tetra-Oacetyl-β--glucopyranosyl)-5a-carba-β--galactopyranose 9.