Developing tools for investigating the cellular activity of glycans will help to delineate the molecular basis for aberrant glycosylation in pathological processes such as cancer. Metabolic oligosaccharide engineering, which inserts sugar-reporting groups into cellular glycoconjugates, represents a powerful method for imaging the localization, trafficking, and dynamics of glycans and isolating them for glyco-proteomic analysis. Herein, we show that the alkyne-reporting group can be incorporated into cellular glycans. The alkyne group is a small, inert, bio-orthogonal handle that can be chemoselectively labeled by using the Cu(I) catalyzed [3 ؉ 2] azide-alkyne cycloaddition, or click chemistry. Alkynyl sugar monomers, based on fucose (Fuc) and N-acetylmannosamine (ManNAc), were incorporated into fucosylated and sialylated glycans in several cancer cell lines, allowing for cell surface and intracellular visualization of glycoconjugates, as well as, observation of alkyne-bearing glycoproteins. Similarly to our previous results with an azido Fuc/alkynyl probe system, we demonstrated that click-activated fluorogenic probes are practical tools for efficiently and selectively labeling alkynyl-modified glycans. Because Fuc and sialic acid are terminal glycan residues with a notably increased presence in many tumors, we hope that our method will provide useful information about their roles in cancer and ultimately can be used for diagnostic and therapeutic purposes.click chemistry ͉ fluorescent imaging ͉ fucose ͉ sialic acid

Protein glycosylation is an important post-translational modification of proteins that has profound effects on structure and function. However, the complex and non-templated nature of glycans has been a barrier to studying many of their basic features, especially on a proteome-wide scale. Here, we introduce a glycoproteomic method, glycoprotein identification and glycan mapping (GIDmap), that tailors the isolation of specific glycoprotein subpopulations based on display of metabolically inserted alkynyl sugar probes that can be selectively manipulated using the bioorthogonal Cu(I)-catalyzed [3 + 2] azide−alkyne cycloaddition. This saccharide-selective glycoprotein immobilization allows for subsequent manipulation and analysis of peptides and glycopeptides by liquid chromatography-tandem mass spectrometry. The power of GIDmap was demonstrated by mapping over 200 N-linked glycosylation sites from glycoproteins isolated from prostate cancer cells treated with an alkynyl sugar derivative of N-acetylmannosamine. Overall, GIDmap is a robust method that will greatly aid in inventorying glycoproteins and mapping glycosylation sites, in addition to providing specific information about saccharide content and glycan behavior.

The first stable 1-germaallene was synthesized by treatment of an extremely hindered alkylidenetelluragermirane with a large excess amount of hexamethylphosphorous triamide or by reductive dechlorination of the corresponding overcrowded (1-chlorovinyl)chlorogermane with t-butyllithium in THF. The germaallene was isolated as a colorless solid by the latter synthetic method and found to be fairly stable even in solution at room temperature, although it underwent an intramolecular cyclization at 80 °C in benzene.

Treatment of an overcrowded diarylgermylene Tbt(Tip)Ge: 1 {Tbt = 2,4,6-tris[bis(trimethylsilyl)methyllphenyl, Tip = 2,4,6-triisopropylphenyl) with carbon disulfide affords the first germaketenedithioacetal derivative 3 as a stable orange crystalline compound, for which the molecular structure is established by X-ray crystallographic analysis.