A Negishi cross-coupling reaction enables the total synthesis of (+)-stachyflin

Asymmetric Total Synthesis of the Naturally Occurring Antibiotic Anthracimycin

“…Carboxylic acid and Weinreb amide derivatives were also inaccessible under numerous conditions; however, ethanethiolate was pleasingly found to mediate auxiliary cleavage of 18, providing thioester 19 in good yield. 17 Stille coupling of 19 with tributyl(vinyl)tin proceeded smoothly, affording diene 20 in excellent yield. Diene 20 was then converted to methyl ester 10 using silver trifluoroacetate; 18 however, treatment of methyl ester 10 with the dianion of 9 (generated either using NaH and n BuLi, or lithium diisopropylamide) resulted only in returned starting material 10 under a range of conditions.…”

“…Meanwhile, treatment of 18 with diisobutylaluminum hydride (DIBAL-H) failed to provide direct access to an aldehyde, instead yielding an intractable mixture of products. Carboxylic acid and Weinreb amide derivatives were also inaccessible under numerous conditions; however, ethanethiolate was pleasingly found to mediate auxiliary cleavage of 18 , providing thioester 19 in good yield . Stille coupling of 19 with tributyl­(vinyl)tin proceeded smoothly, affording diene 20 in excellent yield.…”

“…It was conceived that a more electrophilic coupling partner, such as aldehyde 11, could enable union of these two fragments. Fukuyama reduction 17 of thioester 20 gave rise to a complex, inseparable mixture, presumably resulting from undesired reduction of the diene moiety. Treatment of thioester 20 with DIBAL-H also failed to directly provide aldehyde 11, although the corresponding alcohol was delivered as the major product, with trace formation of desired aldehyde 11.…”

Bio-inspired construction of a tetracyclic ring system with an avarane skeleton: total synthesis of dactyloquinone A

“…The synthesis of avarane sesquiterpenes has been a hot topic because of their unique structure and remarkable biological activity. 5,6 A tricyclic ring system with avarane skeletons was constructed from a Wieland–Miescher ketone derivative ( 7 , Scheme 1a), as depicted in Scheme 1. 5 Recently, Lu et al completed the first total synthesis of dysideanone B ( 12 , Scheme 1a) and dysiherbol A ( 11 , Scheme 1a) through intramolecular radical ring closing and the Heck reaction using the Wieland–Miescher ketone derivative ( 7 ) as the starting material.…”

Asymmetric transfer hydrogenation of prochiral cyclic 1,3-diketones

“…The meroterpenoid stachyflin was derived from (S)-1b prepared by CBS reduction of the diketone with 83% ee, 9 and (S)-1b generated by reduction of the diketone with baker's yeast (>96% ee) 10 served as the pivotal intermediate for the synthesis of the depicted taxol intermediate, 11 stypoldione, 12 and glycinoeclepin A. [13][14][15] (R)-1b is available as well by CBS reduction of the diketone 1,16 or by a multi-step route incorporating a lipase catalyzed desymmetrization that can also be utilized for production of (S)-1b.…”