Synthesis and biological activity evaluation of dolastatin 10 analogues with N-terminal modifications
作者:Xin Wang、Suzhen Dong、Dengke Feng、Yazhou Chen、Mingliang Ma、Wenhao Hu
DOI:10.1016/j.tet.2017.03.006
日期:2017.4
We have described the synthesis of the two complex units (2R,3R,4S)-dolaproine (Dap) and (3R,4S,5S)-dolaisoleuine (Dil) of dolastatin 10 from natural amino acids. The stereoselective syntheses of N-Boc-Dap (4a) and N-Boc-(2S)-iso-Dap (4b) were performed by employing crotylation of N-Boc-l-prolinal as a key step. Barbier-type allylation of N-Boc-l-isoleucinal provided a mild and convenient approach
Stereoselective Synthesis of Isochromanones by an Asymmetric Ortho-Lithiation Strategy: Synthetic Access to the Isochromanone Core of the Ajudazols
作者:Sebastian Essig、Dirk Menche
DOI:10.1021/acs.joc.5b02781
日期:2016.3.4
atropisomeric amide axis for stereocontrol. For direct transformation of sterically hindered amides to isochromanones, efficient and mild one-pot protocols involving either O-alkylation or acidic microwave activation were developed. The procedures may be applied also to highly functionalized as well as stereochemically complex and sensitive substrates and demonstrate a high protective group tolerance
Asymmetric Cross-coupling of Potassium 2-Butenyltrifluoroborates with Aryl and 1-Alkenyl Bromides Catalyzed by a Pd(OAc)<sub>2</sub>/Josiphos Complex
作者:Yasunori Yamamoto、Shingo Takada、Norio Miyaura
DOI:10.1246/cl.2006.1368
日期:2006.12
The asymmetric cross-coupling reaction of [CH3CH=CHCH2BF3]K with aryl or 1-alkenyl bromides selectively occurred at the γ-carbon of 2-butenylborane moiety with regioselectivities in a range of 84–99%. The enantioselectivities were in a range of 77–90%ee when a palladium/CyPF-t-Bu complex was used at 80 °C in the presence of K2CO3 (3 equiv.) in H2O–MeOH (9/1).
Diastereoselective Allylation and Crotylation Reactions of Aldehydes with Potassium Allyl- and Crotyltrifluoroborates under Lewis Acid Catalysis
作者:Robert A. Batey、Avinash N. Thadani、David V. Smil、Alan J. Lough
DOI:10.1055/s-2000-6303
日期:——
Potassium allyl- and crotyltrifluoroborates react with aldehydes in a process catalyzed by a variety of Lewis acids, to give the corresponding homoallylic alcohols. Of the Lewis acids examined, BF3 · OEt2, used either stoichiometrically or catalytically, was found to most efficiently catalyze this reaction. The air and moisture stable potassium organotrifluoroborate salts react with a variety of alkyl, α- or β-substituted alkyl, and aryl aldehydes, and lead to the adducts in high yield and with high diastereoselectivity.
An efficient method for the allylation of aldehydes containing a broad range of functional groups using potassium allyltrifluoroborate is described. The reaction utilizes a catalytic amount of 18-C-6 in biphasic media under open atmosphere and room temperature to provide the corresponding homoallylic alcohols in high yields and without the necessity of any subsequent purification.