220249-55-8Relevant academic research and scientific papers
Studies toward the Synthesis of Amphidinolide C1: Stereoselective Construction of the C(1)-C(15) Segment
Namirembe, Sheila,Yan, Lu,Morken, James P.
, p. 9174 - 9177 (2020)
An enantioselective synthesis of the C(1)-C(15) segment of the marine natural product amphidinolide C has been accomplished by a route that includes a stereoselective boron-Wittig reaction to furnish a trisubstituted alkenylboronate. In addition, the rout
Iridium-catalyzed anti-diastereo- and enantioselective carbonyl (α-trifluoromethyl)allylation from the alcohol or aldehyde oxidation level
Gao, Xin,Zhang, Yong Jian,Krische, Michael J.
supporting information; experimental part, p. 4173 - 4175 (2011/06/20)
A flourish of fluorine: Exposure of α-trifluoromethyl allyl benzoate to alcohols in the presence of an ortho-cyclometalated iridium catalyst results in the generation of aldehyde-allyliridium intermediates to form enantiomerically enriched products of anti-(α-trifluoromethyl)allylation. An identical set of products is obtained from aldehydes under related transfer hydrogenation conditions employing isopropyl alcohol as terminal reductant. Copyright
Direct generation of acyclic polypropionate stereopolyads via double diastereo- and enantioselective iridium-catalyzed crotylation of 1,3-diols: Beyond stepwise carbonyl addition in polyketide construction
Gao, Xin,Han, Hoon,Krische, Michael J.
, p. 12795 - 12800 (2011/10/05)
Under the conditions of transfer hydrogenation employing the cyclometalated iridium catalyst (R)-I derived from [Ir(cod)Cl]2, allyl acetate, 4-cyano-3-nitrobenzoic acid, and the chiral phosphine ligand (R)-SEGPHOS, α-methylallyl acetate engages 1,3-propanediol (1a) and 2-methyl-1,3-propanediol (1b) in double carbonyl crotylation from the alcohol oxidation level to deliver the C2-symmetric and pseudo-C 2-symmetric stereopolyads 2a and 3a, respectively, with exceptional control of anti-diastereoselectivity and enantioselectivity. Notably, the polypropionate stereopentad 3a is formed predominantly as 1 of 16 possible stereoisomers. Desymmetrization of 3a is readily achieved upon iodoetherification to form pyran 4. The direct generation of 3a enables a dramatically simplified approach to previously prepared polypropionate substructures, as demonstrated by the synthesis of C19-C27 of rifamycin S (eight steps, originally prepared in 26 steps) and C19-C25 of scytophycin C (eight steps, originally prepared in 15 steps). The present transfer hydrogenation protocol represents an alternative to chiral auxiliaries, chiral reagents, and premetalated nucleophiles in polyketide construction.
Synthesis and cytotoxicity studies of new cryptophycin analogues
Wen, Lu Liu,Jian, Cun Zhang,Fa, Qin Jiang,Fu, Lei
experimental part, p. 577 - 583 (2009/12/24)
Two analogues of cryptophycin were synthesized and biologically evaluated for their in-vitro cytotoxicities against several solid tumors and leukemia cell lines. The results revealed that both analogues exhibited a broad range of cytotoxic activity with observed IC50 values in the μM-range, and compound 4 was more effective than compound 3 in most assays studied.
An Evans-Tishchenko-ring-closing metathesis approach to medium-ring lactones
Aird, Jennifer I.,Hulme, Alison N.,White, John W.
, p. 631 - 634 (2007/10/03)
A new approach to the synthesis of medium-ring lactones is reported based on sequential Evans-Tishchenko and ring-closing metathesis (RCM) reactions. High diastereoselectivity (>95:5) is demonstrated in the Evans-Tishchenko reaction of unsaturated aldehyd
Stereochemical assignment of the C23-C35 portion of sphinxolide/reidispongiolide class of natural products by asymmetric synthesis
Zampella, Angela,Sepe, Valentina,D'Orsi, Rosa,Bifulco, Giuseppe,Bassarello, Carla,D'Auria, Maria Valeria
, p. 1787 - 1798 (2007/10/03)
The absolute configuration of the seven stereogenic centers contained in the C23-C35 portion of reidispongiolide A is determined by asymmetric synthesis of the corresponding fragment obtained by ozonolysis of the natural macrolide.
Cryptophycin affinity labels: Synthesis and biological activity of a benzophenone analogue of cryptophycin-24
Vidya, Ramdas,Eggen, MariJean,Georg, Gunda I.,Himes, Richard H.
, p. 757 - 760 (2007/10/03)
An efficient synthesis of a C16 side chain benzophenone analogue of cryptophycin-24 using a crotylboration reaction and Heck coupling as key steps is described. In an in vitro tubulin assembly assay, the benzophenone analogue of the β isomer (IC50/s
Total synthesis of cryptophycin-24 (arenastatin A) amenable to structural modifications in the C16 side chain
Eggen,Mossman,Buck,Nair,Bhat,Ali,Reiff,Boge,Georg
, p. 7792 - 7799 (2007/10/03)
Two efficient protocols for the synthesis of tert-butyl (5S,6R,2E,7E)-5-[(tert-butyldimethylsilyl)-oxy]-6-methyl-8-phenyl-2,7-octadie noate, a major component of the cryptophycins, are reported. The first utilized the Noyori reduction and Frater alkylation of methyl 5-benzyloxy-3-oxopentanoate to set two stereogenic centers, which became the C16 hydroxyl and C1' methyl of the cryptophycins. The second approach started from 3-p-methoxybenzyloxypropanal and a crotyl borane reagent derived from (-)-α-pinene to set both stereocenters in a single step and provided the dephenyl analogue, tert-butyl (5S,6R,2E)-5-[(tert-butyldimethylsilyl)oxy]-6-methyl-2,7-octadienoate, in five steps. This compound was readily converted to the 8-phenyl compound via Heck coupling. The silanyloxy esters were efficiently deprotected and coupled to the C2-C10 amino acid fragment to provide desepoxyarenastatin A and its dephenyl analogue. The terminal olefin of the latter was further elaborated via Heck coupling. Epoxidation provided cryptophycin-24 (arenastatin A).
Enantioselective synthesis of a 3'-dephenylcryptophycin synthon
Eggen, MariJean,Georg, Gunda I.
, p. 3177 - 3180 (2007/10/03)
An enantioselective synthesis of tert-butyl (5S,6R)-(E)-5-tert- butyldimethylsilyloxy-6-methyl-2,7-octadienoate, a precursor for the synthesis of the antimitotic macrolides cryptophycin A and arenastatin A (cryptophycin-24), is presented. The key step in the reaction sequence features a crotyl boration that sets both stereocenters that become the C16 hydroxyl and C1' methyl in the cryptophycins. Homologation of the terminal olefin via a Heck reaction is presented.
