Absolute stereostructure and total synthesis of leptomycin B
摘要:
The absolute stereostructure of leptomycin B, an antitumor antibiotic and inhibitor of nuclear protein export, was firstly presumed as 1 having 4S, 5R, 10R, 16R, 18S, 19R, 20S on the basis of NMR comparison with callystatin A (2) and then 1 was asymmetrically synthesized. The synthesized leptomycin B (I) was found identical with the authentic sample in HPLC and CD comparison as well as in other respects. This structural elucidation of the absolute stereostructure and total synthesis are the first example;among the leptomycin family as Streptomyces metabolites. (C) 1998 Elsevier Science Ltd. All rights reserved.
Synthesis of Modified Methyl Furanosides by Intramolecular Oxa-Michael Reaction followed by Pummerer Rearrangement
作者:Diego Gamba-Sanchez、Joëlle Prunet
DOI:10.1021/jo100241e
日期:2010.5.7
A new method is described for the synthesis of ribofuranoses modified at the C3 and C5 positions. The key step is an intramolecular oxa-Michael reaction on a vinyl sulfoxide to install the C2 hydroxy group. The methyl furanosides are obtained by Pummerer rearrangement of the sulfoxide into the corresponding aldehyde, acidic deprotection of the benzylidene acetal, and cyclization.
Sensing Remote Chirality: Stereochemical Determination of β-, γ-, and δ-Chiral Carboxylic Acids
作者:Marina Tanasova、Mercy Anyika、Babak Borhan
DOI:10.1002/anie.201410371
日期:2015.3.27
nonfunctionalizable stereocenters is a challenging task. Presented is a solution in which appropriately substituted bis(porphyrin) tweezers are used. Complexation of a suitably derivatized β‐, γ‐, or δ‐chiralcarboxylicacid to the tweezer induces a predictable helicity of the bis(porphyrin), which is detected as a bisignate Cotton Effect (ECCD). The sign of the ECCD curve is correlated with the absolute
The opening of trans-2-3-epoxy-butan-1-ol derivatives with various organometallicreagents was studied to find the best conditions necessary to obtain convenient yields and regioselectivities for their application in natural product synthesis.
Highly Regioselective Copper-Catalyzed <i>cis</i>- and <i>trans</i>-1-Propenyl Grignard Cleavage of Hindered Epoxides. Application in Propionate Synthesis
作者:David Rodríguez、Marlenne Mulero、José A. Prieto
DOI:10.1021/jo060833t
日期:2006.7.1
Hindered protected and unprotected epoxy alcohols were regioselectively cleaved using copper-catalyzed cis- and trans-1-propenylmagnesium bromide. The reaction exhibited good yield and excellent regioselectivity in systems where organocuprates and organoalanes failed. The cis Grignardreagent displayed no double-bond isomerization, whereas the trans isomer showed partial trans-to-cis equilibration