Synthesis of amphotericin B. 2. fragment C-D of the aglycone

Boschelli, Diane H.; Takemasa, Toshiro; Nishitani, Yasuhiro; Masamune, Satoru

doi:10.1016/s0040-4039(00)95004-4

Cited by 76 publications

(17 citation statements)

References 21 publications

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“…iv. Although some highly (≥98%) stereoselective examples of HWE reaction are known (15,16,(57)(58)(59)(60)(61)(62), it often displays ≤95%, typically 80-90%, stereoselectivity.…”

Section: Resultsmentioning

confidence: 99%

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Wang

Mohan

Negishi

2011

Proc. Natl. Acad. Sci. U.S.A.

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All four stereoisomers (7-10) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (E)-and (Z)-β-bromoacrylates. Although the stereoisomeric purity of the 2Z,4E-isomer (8) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤95%, as reported earlier, the use of CsF or n Bu4NF as a promoter base has now been found to give all of 7-10 in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2E,4E and 2E,4Z isomers of ≥98% purity, but the purity of the 2Z,4E isomer was ≤95%. Mutually complementary HornerWadsworth-Emmons and Still-Gennari (SG) olefinations are also of considerably limited scopes. Neither 2E,4Z nor 2Z,4Z isomer is readily prepared in ≥90% selectivity. In addition to (2Z,4E)-dienoic esters, some (2Z,4E,6E)-and (2Z,4E,6Z)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation-SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (23-30) have been prepared in ≥98% overall selectivity.highly selective synthesis | Pd-catalyzed Negishi coupling A lkenes represent a large number of natural products of bioactive and medicinally important compounds. Of interest in this study are those containing conjugated dienes and oligoenes (1-11) (Fig. 1). Among numerous known methods for the syntheses of alkenes including conjugated dienes and oligoenes (12, 13), carbonyl olefination reactions, notably Wittig olefination (14) and its variants, such as Horner-Wadsworth-Emmons (HWE hereafter) (15, 16), and Still-Gennari (SG hereafter) (17) as well as Ando (18) modifications have been widely used along with related Si-promoted (Peterson) (19) and S-promoted (Julia and Paris) (20) olefination reactions. As useful as these reactions are, they often lack very high (≥98%) stereoselectivity.In search for highly (≥98%) stereoselective alkene synthesis methodology, our attention was initially drawn to alkyne hydroboration, which generally proceeds in >99% syn-selectivity. Following some promising leads of Brown (21) and Zweifel and co-workers (22-25), we reported in 1973 a couple of highly selective routes to 1,4-disubstituted (E,E)-and (E,Z)-1,3-dienes (1, 3, 26), which appear to represent the earliest syntheses of unsymmetrically substituted conjugated dienes in very high (≥97%) selectivity via organometallic alkenylation.Despite highly selective and satisfactory results described above, our continued search for a more generally applicable and straightforward route to conjugated di-and oligoenes led to the discovery in 1976 of the Pd-catalyzed alkenyl-alkenyl coupling with alkenylalanes (27) and subsequently with alkenyl derivatives containing Zr (28) and Zn (29), collectively known as Negishi coupling (30,31). Along with the subsequently developed alkenylboron version (Suzuki coupling) (32-34), the Pd-catalyzed alken...

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“…iv. Although some highly (≥98%) stereoselective examples of HWE reaction are known (15,16,(57)(58)(59)(60)(61)(62), it often displays ≤95%, typically 80-90%, stereoselectivity.…”

Section: Resultsmentioning

confidence: 99%

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Wang

Mohan

Negishi

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…For example, E,E,E-1,8-hexatrienoate derivatives have been prepared by photochemical, [16] E,E,E,E-1,10-hexatetraenoic acid has been prepared by alkyne or tetraene isomerisation, as have the corresponding penta-and hexa-ene analogues, [17] and by using Wittig-related methods. [18] In Scheme 1. Proposed mechanistic scheme for the reductive dimerisation of terminal, electron-deficient iodoalkenes exemplified by Z-iodoacrylate 1.…”

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confidence: 99%

A Stereoselective Palladium‐Mediated Reductive Coupling of Electron‐Deficient Terminal Iodoalkenes

et al. 2008

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Iodoacrylate esters undergo palladiumcatalysed reductive homocoupling to derive dienyl diester derivatives. This reductive coupling can be extended to ester-substituted terminal iododienes to derive tetraene diesters. In all cases, the reactions show relatively high levels of stereocontrol, which shows an inversion of stereochemistry about one iodoalkene unit. This process, and the suggestion that the reaction releases diiodine, is consistent with a syn-1,2-addition of an iodopalladium(II)-alkene species across another iodoalkene unit (carbometallation step), followed by reductive syn-elimination of iodopalladium iodide to derive palladium(II) iodide. It appears that under the reaction conditions employed, palladium(II) iodide may equilibrate to palladium(0) and diiodine, which can be observed or trapped out from the reaction mixture.

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“…(iv) Although some highly (≥98%) stereoselective examples of HWE reaction are known [110][111][112][113][114], it often displays ≤95%, typically 80-90%, stereoselectivity. In contrast with frequently less than highly (≥98%) selective HWE olefination discussed above, SG olefination represented by Eq.…”

Section: Critical Analysis Of the Current Scope And Limitations Of Homentioning

confidence: 99%

Pd‐Catalyzed Cross‐Coupling with Organometals Containing Zn, Al, Zr, and so on – The Negishi Coupling and Its Recent Advances

Kamada

Kim

et al. 2013

Metal‐Catalyzed Cross‐Coupling Reactions and More

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The Pd-or Ni-catalyzed cross-coupling reactions of organometals containing Zn, Al, Zr, and B as well as related reactions of those containing Mg and several other metals collectively have emerged as arguably the most widely applicable organic skeleton construction method discovered and developed over the past several decades, allowing synthetic chemists to prepare practically all types of organic compounds. In this chapter, some of the seminal and critically important discoveries and early developments in the 1970s as well as their current scope are briefly discussed. Some of the notable discoveries and developments include (i) identification of superior properties of Pd as a critical element for crosscoupling relative to Ni, (ii) the broad scope of Pd-or Ni-catalyzed cross-coupling with respect to metal countercations including Zn, Al, Zr, B, and Mg, (iii) the hydrometallation-Pd-catalyzed cross-coupling sequential processes for selective syntheses of alkenes, dienes, oligoenes, and oligoenynes, (iv) double metal catalysis involving Pd or Ni and added metal compounds containing Zn, In, Li, and others, and (v) realization of high turnover numbers (TONs) (≥10 3 -10 9 ) through the use of chelating phosphines, such as bis-[2-(diphenylphosphino)phenyl] ether (DPEphos) and 1,1 -Bis(diphenylphosphino)ferrocene (dppf).The Zr-catalyzed alkyne carboalumination and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction) have provided efficient and selective routes to (E)-trisubstituted alkenylalanes and 2-substituted chiral alkylalanes, respectively. These reactions provide two additional examples of prototypical transition metal-catalyzed organometallic reactions. Significantly, they can be readily combined with the Pd-or Ni-catalyzed cross-coupling for the synthesis of trisubstituted alkenes embracing a wide variety of natural products, such as terpenoids, carotenoids, and others, as well as various chiral organics including deoxypolypropionates and saturated terpenoids. The Zr-catalyzed alkyne carboalumination has been applied to the synthesis of a large number (>100) of natural products, while the ZACA reaction has been transformed from a mere scientific novelty to a full-fledged asymmetric synthetic method that is catalytic in both transition metal (Zr) and chiral auxiliaries through a series of breakthroughs.

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Synthesis of amphotericin B. 2. fragment C-D of the aglycone

Cited by 76 publications

References 21 publications

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

A Stereoselective Palladium‐Mediated Reductive Coupling of Electron‐Deficient Terminal Iodoalkenes

Pd‐Catalyzed Cross‐Coupling with Organometals Containing Zn, Al, Zr, and so on – The Negishi Coupling and Its Recent Advances

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