Silicon-containing amino acids preparation

Successful sila-modification of several peptides leading to new protease inhibitors (03CODD526) stimulated the elaboration of synthetic methods for the preparation of silicon-containing amino acids. Among these compounds a-amino acids-containing silacycles were synthesized... 

In general, sila-heterocycles are believed to be promising candidates for the development of silicon-based dmgs and agrochemicals. For example, the sila-proline ester 184 was prepared as part of a systematic study of silicon-containing amino acids and proteins <2000JOM19>. 

Functionally-substituted disilanes are useful starting materials for silylenes, silicon containing heterocycles or for polymeric silicon-containing materials. The classical method to prepare functionalized disilanes is the cleavage of aryl groups by HCI/AICI3 [1] or by triflic acid [2]. An easier method is the introduction of chloro- or alkoxygroups by replacement of amino substituents. 

Preparation of Silicon- and Germanium-Containing a-Amino Acids... 

Dimethyl-2-oxazoline is commercially available from Columbia Organic Chemicals, 912 Drake Street, Columbia, South Carolina, or may be prepared as follows. In a 250-ml., three-necked flask is placed 89.14 g. (1.0 mole) of 2-amino-2-methyl-l-propanol, and the flask is cooled in an ice bath. The amine is carefully neutralized with 52.3 g. (1.0 mole) of 90.6% formic acid over a 1-hour period. A magnetic stirring bar is added, the flask is fitted with a short path distillation head, and the reaction mixture is placed in a silicon oil bath which is rapidly heated to 220-250°. The azeotropic mixture of water and oxazoline distills over a period of 2-4 hours and is collected in an ioe-cooled flask containing ether. The aqueous layer is separated, saturated with sodium chloride, and extracted with three 50-ml. portions of ether. The combined ethereal extracts are dried over potassium carbonate, filtered to remove the drying agent, and the ether is removed at 35-40° at atmospheric pressure. The 4,4-dimethyl-2-oxazoline is collected as the temperature rises above 85°. The yield is 56.7-62.7 g. (57—63%) of a colorless mobile liquid, b.p. 99-100° (758 mm. Hg). 

By using intermediates that contain nitrogen, silicone, and other different type atoms, it has been possible to prepare a variety of unsaturated polyesters, containing amide, amino, urethane, siloxane, and other heteroatom residues. Unsaturated polyesters containing amide moieties can be prepared by several techniques. MA and fumaric acid have also been utilized for prepar-... 

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