Highly Diastereoselective Oxy‐Michael Additions of Enantiopure δ‐Lactol Anions to Nitroalkenes: Asymmetric Synthesis of 1,2‐Amino Alcohols.

Abstract

Amino alcohols Amino alcohols Q 0240Highly Diastereoselective Oxy-Michael Additions of Enantiopure δ-Lactol Anions to Nitroalkenes: Asymmetric Synthesis of 1,2-Amino Alcohols. -In situ generated "naked" alkoxide of 6-methyl-δ-lactol (I) is used for diastereoselective oxy-Michael addition reactions to a range of nitroalkene acceptors to give O-protected Henry products. Reduction of the nitro group and acidic methanolysis of the tetrahydropyran group affords enantiomerically enriched 1,2-amino alcohols. -(ADDERLEY, N. J.; BUCHANAN, D. J.; DIXON*, D. J.; LAINE, D. I.; Angew. Chem., Int. Ed. 42 (2003) 35, 4241-4244; Dep. Chem., Univ. Cambridge, Cambridge CB2 1EW, UK; Eng.) -S. Adam 52-082

The convergent total synthesis and antibacterial profile of the natural product streptothricin F

“…[39][40][41] Nitro reduction through generation of nickel boride followed by immediate addition of di-tert-butyl dicarbonate in one pot produced dicarbamate 12 as a mixture of diastereomers. 42,43 Warming in formic acid deprotected the previously installed Boc group and promoted lactamization to afford 13, where the diastereomeric mixture could be separated. Silylation of 13 with TBS triflate, followed by hydrogenation to remove benzyl carbamate and subsequent Boc protection produced dicarbamate lactam 4 in good yield over three steps.…”

Organocatalytic Name Reactions Enabled by NHCs

“…It takes place between active methylene with α,β-unsaturated carbonyl compound, leading to C-C bond formation. Furthermore, asymmetric Michael addition has been known since the 1980s [ 144 , 145 , 146 , 147 , 148 , 149 ]. In addition, the umpolung effect forced by imines is known to take place in this type of synthesis [ 150 ].…”

Lyngbouilloside and Related Macrolides from Marine Cyanobacteria

“…The resulting lactone was then reduced with DIBAL-H to the corresponding hemiketal 10, which was obtained as a mixture of two diastereomers (dr = 1.5:1) in 87% overall yield. Deprotonation of the resulting -lactol with KHMDS in the presence of 18-crown-6 [14] afforded the corresponding alkoxide which underwent a highly diastereoselective methylation to ketal 11. A few subsequent steps allowed to set the terminal olefin and convert the dithiol moiety to the corresponding ketone 12, while reduction with sodium borohydride introduced the C5 stereogenic center and generated 13 as a single diastereomer in 99% yield.…”