The three-step manufacturing process used in the synthesis of tenofovir disoproxil fumarate (1) was studied and optimized, leading to a more productive and robust process. The yield was improved from about 13% overall to 24%. Key process improvements identified included implementation of a telescoped process for the second stage that obviated the need for an extraction and solvent exchange, and significant optimization of the final reaction, including the beneficial effect of adding a quaternary ammonium salt to the alkylation reaction and development of a nonaqueous process for removal of NMP and triethylamine from the product mixture to decrease the level of decomposition of product during the isolation.

This paper describes a novel supported Weinreb amide resin that facilitates parallel synthesis of aldehydes and ketones on a scale useful for chemical library synthesis. This new resin makes it possible to produce custom aldehydes and ketones from a wide range of carboxylic acids, including N-BOC-amino acids. A variety of commercially unavailable aldehydes are easily synthesized in parallel and obtained in high purity via a simple filtration workup, thus facilitating parallel synthesis of lead optimization libraries that typically require custom synthesis of aldehyde intermediates for development of structure-activity relationships. To demonstrate the utility of this method, we synthesized a small library based on a supported Horner-Emmons reagent. This is the first time it has been shown that aldehydes generated via a supported Weinreb amide could be used directly as reagents in chemical library synthesis employing moisture-sensitive reactions. The analogous solution reaction is not suited for parallel synthesis because of the laborious extractive workup procedure necessary and, at times, the instability of these reactive intermediates.

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