An Improved Approach to Chiral Cyclopentenone Building Blocks. Total Synthesis of Pentenomycin I and Neplanocin A
作者:John K. Gallos、Christos I. Stathakis、Stefanos S. Kotoulas、Alexandros E. Koumbis
DOI:10.1021/jo050987t
日期:2005.8.1
An improved approach to enantiomerically pure hydroxylated cyclopentenones is reported here, which involves intramolecular nitrone cycloaddition of sugar-derived chiral pent-4-enals and hex-5-en-ones-2 followed by N−O bond cleavage, quaternization of the amine thus produced, and finally oxidative elimination of the amino group. Synthesis of pentenomycin I and neplanocin A is described following this
Transition-Metal-Mediated Cascade Reactions: The Water-Accelerated Carboalumination−Claisen Rearrangement−Carbonyl Addition Reaction
作者:Peter Wipf、David L. Waller、Jonathan T. Reeves
DOI:10.1021/jo051211v
日期:2005.9.1
water-accelerated catalytic carboalumination, a Claisen rearrangement, and a nucleophilic carbonyl addition converts terminal alkynes and allyl vinyl ethers into allylic alcohols containing up to three contiguous asymmetric carbon centers. Stoichiometric quantities of water as an additive increase the rate of the [3,3] sigmatropicrearrangement as well as the diastereoselectivity of the carbonyl addition
Mn(III)-based oxidative free-radical cyclizations of alkenyl Meldrum's acids
作者:Barry B. Snider、Rachel B. Smith
DOI:10.1016/s0040-4020(01)01054-7
日期:2002.1
Oxidativecyclization of unsaturated Meldrum's acids can be carried out at temperatures as low as −30°C. The rate-determining step is cyclization of the enolate to the alkene (11 to 14 and 15) rather than enolization, which is the rate-determining step with dimethyl 4-pentenylmalonate (1). While cyclization of 1 gives mainly cyclopentanes, cyclization of Meldrum's acids provides a versatile route to
A Bicyclo[3.2.0]hept-3-en-6-one Approach to Prostaglandin Intermediates
作者:Emanuela Marotta、Paolo Righi、Goffredo Rosini
DOI:10.1021/ol006664v
日期:2000.12.1
6-benzyloxymethyl-7-hydroxy-2-oxabicyclo [3.3.0]octan-3-one (1), a Corey lactone derivative, and 6-exo-benzyloxymethyl-2-oxabicyclo[3.3. 0]oct-7-en-3-one (2), have been obtained stereoselectively through the bicyclo[3.2.0]hept-3-en-6-one approach via 5-benzyloxymethyl-3-hydroxy-6-heptenoic acid, easily accessible from the inexpensive monoprotected cis-2-butene-1,4-diol.