A Highly Stereoselective and Flexible Strategy for the Convergent Synthesis of Long‐Chain Polydeoxypropionates: Application towards the Synthesis of the Glycolipid Membrane Components Hydroxyphthioceranic and Phthioceranic Acid

Pischl, Matthias; Weise, Christian F.; Haseloff, Stefan; Müller, Marc-André; Pfaltz, Andreas; Schneider, Christoph

doi:10.1002/chem.201404034

Cited by 18 publications

(12 citation statements)

References 78 publications

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“…Treatment of 9 with LiBH 4 reductively cleaved the chiral auxiliary, and the protection of the hydroxyl group using 4‐methoxybenzyl (PMB) imidate provided alkenyl iodide 10 in good overall yield. B ‐Alkyl Suzuki‐coupling reaction of the alkenyl iodide 10 with alkyl iodide 6 , provided alkene 11 in excellent yield . Finally, the removal of the TBS‐protecting group and subsequent conversion to the alkyl iodide 5 proceeded smoothly.…”

Section: Methodsmentioning

confidence: 98%

Enantioselective Synthesis of the Northwestern Fragment of Tausalarin C

Joo

Lee

Pyun

et al. 2018

Bulletin Korean Chem Soc

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Tausalarin C (1a) (Figure 1), a structurally unique 12-and 17-membered bismacrolide ring with an inhibitory effect against the growth of human leukemic cell line K562 in a micromolar range, was first isolated from the Madagascan sponge Fascaplysinopsis species in 2009. 1a Biosynthesis of tausalarin C (1a) was also proposed by an assembly of salarin A and pre-taumycin A.1b,c Recently, synthesis and revision of relative stereochemistry in 12-ring skeleton of taumycin A (1b) were reported by Maio and deGruyter. 2 We report herein the enantioselective synthesis of the northwestern fragment 2 of tausalarin C (1a) where the stereochemistry at C 9 00 was chosen arbitrarily. Retrosynthetic analysis for fragment 2 is shown in Scheme 1. The fragment 2 would be prepared by esterification of t-butyl ester 3, amide coupling, and intramolecular cyclization. Palladium-mediated Suzuki cross-coupling reaction of alkenyl iodide 4 and alkyl iodide 5 might be employed to afford the ester 3. Evans asymmetric aldol reaction and Suzuki-coupling reaction would provide the iodide 5 from a known alkyl iodide 6 and but-2-ynal 7.The synthesis of alkyl iodide 5 is summarized in Scheme 2. An alcohol 8 was readily prepared by Evans asymmetric aldol reaction with auxiliary 12 and aldehyde 7 in 90% yield.3 t-Butyldimethylsilyl (TBS) protection of the alcohol 8 with t-butyldimethylsilyl triflate (TBSOTf) in the presence of 2,6-lutidine at −40 C occurred successfully without epimerization. Palladium-catalyzed hydrostannylation yielded an alkenyl tin intermediate with reasonable regioselectivity (9:1) 4 in good yield, and subsequent tin-iodine exchange furnished alkenyl iodide 9. Treatment of 9 with LiBH 4 reductively cleaved the chiral auxiliary, and the protection of the hydroxyl group using 4-methoxybenzyl (PMB) imidate provided alkenyl iodide 10 in good overall yield. BAlkyl Suzuki-coupling reaction of the alkenyl iodide 10 with alkyl iodide 6, 5 provided alkene 11 in excellent yield. 6Finally, the removal of the TBS-protecting group and subsequent conversion to the alkyl iodide 5 proceeded smoothly. Then, we shifted our focus to the alkenyl iodide 4 (Scheme 3). Treatment of Weinreb amide 12 with 1-propynylmagnesium bromide provided alkyne 13 in good yield.7 NaBH 4 reduction and subsequent protection of amino alcohol moiety generated alkyne 14. Hydrozirconation/iodination protocol using Schwartz reagent provided the desired alkenyl iodide 4. 8With subunits 4 and 5 in hand, we then examined palladium-mediated C─C coupling reaction (Scheme 4). Fortunately, Suzuki-coupling reaction proceeded successfully to afford compound 15 in 83% yield. Subsequent cleavage of the PMB-protecting group of 15, oxidation of the liberated hydroxyl group, addition of the lithium enolate of t-butyl acetate, Dess-Martin Periodinane (DMP) oxidation, and removal of the silyl moiety provided the key intermediate 3. Conversion of 3 into the precursor 16 was Figure 1. Structures of tausalarin C (1a) and taumycin A (1b).Scheme 1. Retrosynthetic analysis for fragment 2.

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Section: Methodsmentioning

confidence: 98%

Enantioselective Synthesis of the Northwestern Fragment of Tausalarin C

Joo

Lee

Pyun

et al. 2018

Bulletin Korean Chem Soc

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“…For the shorter of the two routes, this ultimately enabled access to 5 in only 11 or 12 steps (see below) and with almost perfect atom economy 22. 23…”

Section: Methodsmentioning

confidence: 99%

Directed Hydrogenations and an Ireland–Claisen Rearrangement Linked to Evans–Tishchenko Chemistry: The Highly Efficient Total Synthesis of the Marine Cyclodepsipeptide Doliculide

Chen

Altmann

2015

Chemistry A European J

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Two new convergent total syntheses have been developed for the cytotoxic, actin microfilament-stabilizing marine cyclodepsipeptide doliculide (1). A key strategic element of both routes is the establishment of the central stereogenic center of the characteristic polydeoxypropionate stereotriad by means of a hydroxyl-directed catalytic hydrogenation of a trisubstituted double bond. The requisite olefin substrates were obtained through a modified Suzuki-Miyaura coupling or through Ireland-Claisen rearrangement of a propionate ester, respectively; the latter was the direct result of a highly selective Evans-Tishchenko reduction of a hydroxy ketone that had been obtained in a stereoselective Paterson aldol reaction. Doliculide (1) was finally obtained in a total number of 17 or 15 (14) linear steps, respectively, which represents a substantial improvement over previous syntheses of this highly bioactive natural product.

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“…Interestingly, almost all polymers in this list were prepared using Pd(PPh 3 ) 4 or Pd(OAc) 2 as catalysts [164,165,166,167,168,169,170,171,172], although there are some exceptions [173,174,175,176,177,178]. Focussing more in the catalyst employed and carrying out a catalyst screening for a specific polymerization is gradually becoming more and more common [139,140,141,142,143,144,145,146,147,148,149,150,179,180,181].…”

Section: Applicationsmentioning

confidence: 99%

Recent Developments in the Suzuki-Miyaura Reaction: 2010–2014

2015

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Abstract:The Suzuki-Miyaura reaction (SMR), involving the coupling of an organoboron reagent and an organic halide or pseudo-halide in the presence of a palladium or nickel catalyst and a base, has arguably become one of most utilized tools for the construction of a C-C bond. This review intends to be general account of all types of catalytic systems, new coupling partners and applications, including the

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A Highly Stereoselective and Flexible Strategy for the Convergent Synthesis of Long‐Chain Polydeoxypropionates: Application towards the Synthesis of the Glycolipid Membrane Components Hydroxyphthioceranic and Phthioceranic Acid

Cited by 18 publications

References 78 publications

Enantioselective Synthesis of the Northwestern Fragment of Tausalarin C

Enantioselective Synthesis of the Northwestern Fragment of Tausalarin C

Directed Hydrogenations and an Ireland–Claisen Rearrangement Linked to Evans–Tishchenko Chemistry: The Highly Efficient Total Synthesis of the Marine Cyclodepsipeptide Doliculide

Recent Developments in the Suzuki-Miyaura Reaction: 2010–2014

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