Caesium bicarbonate

This new approach involved alkylation of methyl 4-hydroxybenzoate with (354) using caesium bicarbonate as the acid scavenger [174]. The resulting amide ester (356) was sequentially deprotected and saponified to produce (357). Incorporation of the glutamic acid moiety was best accomplished using solid-phase peptide synthesis techniques and gave consistently better overall yields of (358) [102, 177]. 

The chemical reactions to conjugate amino acids or peptides with polystyrenes and other supports naturally depend on the type of functional sites on the gel phase. In most cases, chloromethyl groups are used to bind the starting N-protected amino acid - which is the C-terminal one of the target sequence to be synthesized — to the insoluble but swollen polymer. To date this is most efficiently done by utilizing caesium salts of the carboxylic components [84], which are simply prepared with caesium bicarbonate or hydroxide. To prevent base catalyzed racemization and side reactions on the polymer like saponification of ester bonds or of chloromethyl functions by caesium hydroxide not neutralized, N-pro-tected amino acids are used in a slight excess. 

Lithium carbonate is so sparingly soluble as to be precipitated from solutions of lithium salts by sodium carbonate. It dissolves in water containing carbon dioxide but there is no direct evidence that a bicarbonate is formed. The bicarbonates of the other alkali metals may all be obtained in solid form. Those of rubidium and caesium are more soluble and thermally stable than the sodium and potassium salts. 

The alkali salts include carbonates, bicarbonates, phosphates, sulphides, bisulphides, silicates, bisulphites, aluminates, hydroxides, acetates, tungstenates, etc. of sodium, potassium, rhodium and caesium. Suitable hydrogenation/ dehydrogenation components can be elements of group V-B, VI-B or group VIII,... 

N-AUcylation of l,2,4-Dithiazolidine-3,5-dione (1). The very low piifa value of 1 (p/fa = 2.85 ) compared with other imides such as phthalimide (typically ca. 9.5-10) facilitates 7V-deprotonation with a wide range of bases. These include sodium or potassium hydride, sodium acetate, sodium bicarbonate, potassium tert-butoxide, and caesium carbonate. The optimum stoichiometry of 1 to base is dependent on the base and alkyl halide in question, with acetonitrile proving to be the preferred solvent (eq 6). ... 

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