Stereochemical elucidation of the 1,4 polyketide amphidinoketide I
作者:Louise M Walsh、Jonathan M Goodman
DOI:10.1039/b309104j
日期:——
The relative and absolute stereochemistry of amphidinoketide I has been determined by the total synthesis of all the diastereoisomers. Molecular modelling suggests that the natural product is not the thermodynamically preferred diastereoisomer.
An Effective Bifunctional Aldehyde Linchpin for Type II Anion Relay Chemistry: Development and Application to the Synthesis of a C16–C29 Fragment of Rhizopodin
作者:Bruno Melillo、Ming Z. Chen、Roberto Forestieri、Amos B. Smith
DOI:10.1021/acs.orglett.5b03235
日期:2015.12.18
The design, synthesis, and validation of a new bifunctional aldehyde linchpin for Type II anionrelaychemistry have been achieved. For this linchpin, the initial nucleophilic addition proceeds under Felkin–Anh control to generate the syn-alkoxide, which undergoes a 1,4-Brook rearrangement to relay the negative charge, thus leading to the formation of a dithiane-stabilized carbanion. Subsequent trapping
was realized by the substrate-controlled crotylation of β-branched α-methylaldehydes with potassium crotyltrifluoroborates. Especially, crotylation of 2-(1,3-dithian-2-yl)propanal with potassium (E)-crotyltrifluoroborate afforded, in good yield and with excellent diastereoselectivity, a useful buildingblock that has different and potential functional groups on both ends.
Room-Temperature Metallation of 2-Substituted 1,3-Dithiane Derivatives and Subsequent Coupling with 2,3-Disubstituted Oxiranes
作者:Mitsuaki Ide、Masaya Nakata
DOI:10.1246/bcsj.72.2491
日期:1999.11
2-Substituted 1,3-dithiane derivatives, (S)-1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)propane (9), (S)-1-(t-butyldimethylsiloxy)-2-(1,3-dithian-2-yl)propane, 1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)-2-methylpropane, and 1,2-bis(t-butyldiphenylsiloxy)-3-(1,3-dithian-2-yl)propane, were subjected to lithiation in THF with n-BuLi at room temperature (r.t.); the resulting anions reacted with 2,3-disubstituted oxirane, trans-2-methyl-3-(triphenylmethoxymethyl)oxirane (22), at r.t., giving the coupling products in satisfactory yield. On the other hand, the lithium salt formed in ether from (S)-2-(1,3-dithian-2-yl)-1-(4-methoxybenzyloxy)propane with n-BuLi at r.t. reacted with 22 at r.t. in the presence of hexamethylphosphoric triamide to afford the coupling product in moderate yield. In addition, a mixed organometallic reagent, n-BuLi / Bu2Mg, was found to be an effective metallation reagent for 9 and the resulting anion reacted with 22 to afford the coupling product in good yield.
A Stereoselective Formal Synthesis of Quinolizidine (-)-217A
作者:Hosam Choi、Jiyong Hong、Kiyoun Lee
DOI:10.1002/ejoc.201901680
日期:2020.2.14
Reported herein is a highly stereoselective formal synthesis of quinolizidine (–)‐217. The central feature of the approach is the combination of a dithiane coupling reaction and an organocatalytic aza‐conjugate addition reaction that provides the functionalized trisubstituted 2,6‐cis‐piperidine ring system in a diastereoselective manner.