ABSTRACT
A cross aldol reaction between [(S)-(-)] or [(R)-(+)]-benzyloxypropanal and silyl enol ethers derived from bicyclo[3.2.0]alkanones was carried out in the presence of TiCl4, leading with total stereoselectivity to a 1 : 1 mixture of enantiomerically pure diastereomers isolated in 81% overall yield. Thus, 5 stereogenic centers could be created starting from one. Furthermore, an efficient access to an enantiomerically pure tricyclo[5.3.0.0(2,6)]decane scaffold was possible via a 4 step reaction sequence.
Subject(s)
Alcohols/chemical synthesis , Ethers/chemical synthesis , Ketones/chemistry , Alcohols/chemistry , Crystallography, X-Ray , Ethers/chemistry , Models, Molecular , Molecular Structure , StereoisomerismABSTRACT
The combination of a modular assembly of enantiopure triynes and a powerful rhodium-catalyzed [2 + 2 + 2] alkyne cyclotrimerization reaction opens new and efficient entries to a set of alcyopterosins, including the first total synthesis of the alcyopterosins L, M, and C.
Subject(s)
Sesquiterpenes/chemical synthesis , Catalysis , Cyclization , Molecular Structure , Rhodium/chemistryABSTRACT
tert-Butyldimethylsilyltriflate (TBSOTf)/NEt(3) treatment of alkynyl esters tethered to bicycloalkanones led to tricyclic allenoates with total diastereoselectivity for the ring junction. The allenoates result from an intramolecular alkynylogous Mukaiyama aldol reaction promoted by a TBSOTf/NEt(3) dual activation, with key intermediates of silylalkynylketene acetals. This novel methodology was illustrated by a formal total synthesis of (+/-)-hamigeran B.
