Stereodivergent Dual Catalytic α‐Allylation of Protected α‐Amino‐ and α‐Hydroxyacetaldehydes
作者:Tobias Sandmeier、Simon Krautwald、Hannes F. Zipfel、Erick M. Carreira
DOI:10.1002/anie.201506933
日期:2015.11.23
Fully stereodivergentdual‐catalyticα‐allylation of protectedα‐amino‐ and α‐hydroxyacetaldehydes is achieved through iridium‐ and amine‐catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99 % ee, and with d.r. values greater than 20:1 in some cases. Additionally
An Unprecedented Silver Salt Effect Switches the Facial Selectivity in the Vinylogous Mukaiyama Aldol Reaction
作者:Yufan Liang、Lin Wang、Rong Zhu、Lujiang Deng、Yunfang Yang、Junmin Quan、Jiahua Chen、Zhen Yang
DOI:10.1002/adsc.201000420
日期:2010.10.4
Silver hexafluroantimonate was identified as a highly efficient agent to reverse the facial selectivity of the titanium chloride-mediated vinylogous Mukaiyama aldol reaction (VMAR), and this unprecedented reaction provides a concise, diastereoselective synthesis of δ-hydroxy-α,γ-dimethyl-α,β-unsaturated carbonyl units from readily available chiral vinylketene silyl N,O-acetal 6 and ethyl glyoxylate
Synthesis of 4,4-difluoroglycosides using ring-closing metathesis
作者:Christophe Audouard、John Fawcett、Gerry A. Griffiths、Jonathan M. Percy、St�phane Pintat、Clive A. Smith
DOI:10.1039/b313731g
日期:——
direct sequence involving ring-closingmetathesis and indium-mediated difluoroallylation with 1-bromo-1,1-difluoropropene in water. Two protecting group strategies were explored, one to allow protection of the primary C-6 hydroxyl group throughout the sequence, while the second was intended to allow deprotection after RCM and before dihydroxylation. The benzyl ether could be used in the first role, and
Enantioselective synthesis of β-amino alcohols and α-amino acids via a copper catalyzed addition of diorganozinc reagents to N-phosphinoylimines
作者:Jean-Nicolas Desrosiers、Alexandre Côté、André B. Charette
DOI:10.1016/j.tet.2005.03.113
日期:2005.6
Enantioenriched β-amino alcohols were prepared via an asymmetric addition of diethylzinc, catalyzed by the BozPHOS·Cu(I) complex, on in situ formed N-phosphinoylimines. The nature of the hydroxyl protecting groups was found to affect the enantioselectivities. Subsequent deprotection and oxidation of N-phosphinoyl β-amino alcohols afforded opticallyactiveα-aminoacids (97% ee).
anal and 3-buten-2-one followed by desilylation gave rise to the corresponding α-methylene-β,γ-dihydroxy ketone further converted by reductive ozonolysis of the carbon–carbon double bond into racemic 4,5-dihydroxy-2,3-pentanedione (DPD), a significant molecule in bacterial cell–cell communication systems. The same sequence applied to other substrates allowed the preparation of chain elongated analogues