Silyl ethers reagent, aided

In the first step the cyclic acetal is subjected to acid cleavage, after which all the free alcohol functions are protected as TBS ethers with the aid of the very reactive silylation reagent I BS triflate. The primary alcohol is then deprotected under mild conditions and oxi-di/ed with FDC to a carboxylic acid. 

The respective introducing reagents may also be sterically more demanding and give better selecti-vities in the protection of polyfunctional molecules. This is mainly exploited in nucleotide chemistry. Also, stereochemical bias may be introduced with the aid of appropriate silyl protection. As shown in equation (16), tribenzylsilyl and tri-p-xylylsilyl ethers were used to control the stereochemistry of epoxi-dation in prostaglandin syntheses. ... 

The introduction of an azide functionality with CAN/NaNs as the reagents has been shown to be a useful transformation in organic synthesis. It also offers a convenient protocol for the bis-functionalization of a variety of alkenes. " The treatment of silyl enol ethers with sodium azide and CAN gives the a-azido ketones. The reactions of (substituted)styrenes with sodium azide and CAN in methanol under oxygenated conditions also furnish a-azido ketones (eq 21). With the aid of sodium iodide. 

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