The synthetic strategy for producing multigram quantities of (+)-discodermolide (1) using a hybridized Novartis−Smith−Paterson synthetic route via common precursor 3 is described. In the first part of this five-part series, we present a multikilogram preparation of α-methyl aldehyde 10 from Roche ester, its syn-aldol reaction with Evans boron enolate, removal of the chiral auxiliary, and the preparation of Weinreb amide 3 (Smith common precursor). The common precursor was produced without any chromatography.

Smith's procedure of preparing fragment C15 - 21 (5) from common precursor 3 was optimized. The ease of plant operations made this six-step route successful for the production of several kilograms of this fragment with high purity.

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A practical and robust process for the synthesis of an Isatoribine pro-drug was demonstrated. The process relies on a streamlined glycosylation carried out in xylene and an effective regioselective enzymatic hydrolysis that can be run in a semicontinuous way. Analysis of the process mass intensity established the high impact from an environmental standpoint of our process improvement.

A practical and robust process for the derivatization of Cyclosporin A was demonstrated. The processes rely on the opening of Cyclosporin A and removal of amino acid fragments via Edman degradation, with the isolation of crystalline tetrafluoroboric salts of the corresponding acyclic polypeptides.