Macrolactone Stille coupling reaction

Key steps (Figure 3.3, Scheme 3.2) in the Nicolaou synthesis of ABJ879 (10) are the formation of the C12-C13 double bond via a selective Wittig reaction between phosphorane 11 and aldehyde 12, the stereoselective aldol reaction of ot-chiral aldehyde 13 and ketone 14, macrolactonization of seco acid 16, stereoselective Sharpless epoxidation, to afford the C12-C13 epoxide, and introduction of the heterocycle by means of Stille coupling. ... 

A Mitsunobu process simultaneously coupled the enyne acid fragment 4 to /J-lactam 10 and inverted the CIO stereochemistry to the required (S)-configured ester 11 in 93% yield. A deprotection provided alcohol 12, the key /J-lactam-based macrolactonization substrate, which, under conditions similar to those reported by Palomo for intermolecular alcoholysis of /J-lactams (Ojima et al, 1992, 1993 Palomo et al, 1995), provided the desired core macrocycle 13 of PatA 13 (Hesse, 1991 Manhas et al, 1988 Wasserman, 1987). Subsequent Lindlar hydrogenation gave the required E, Z-dienoate. A Stille reaction and final deprotection cleanly provided (-)-PatA that was identical in all respects to the natural product (Romo etal, 1998 Rzasaef al, 1998). This first total synthesis confirmed the relative and absolute configuration of the natural product and paved the way for synthesis of derivatives for probing the mode of action of this natural product. 

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