Short total syntheses of both the putative and actual structures of the clerodane diterpenoid (+/-)-sacacarin by double annulation.
[reaction: see text] The putative structure of the naturally occurring clerodane diterpenoid (+/-)-sacacarin has been prepared in only 10 steps, six of which are C-C bond-forming steps, in a chemo-, regio-, and diastereoselective manner. The key part of the synthesis is the double annulation (double Michael, Pinner, and Dieckmann reaction) of a tethered carbon diacid and 3-butyn-2-one. A corrected structure for sacacarin is proposed, and the structure is proven by synthesis.
Nitro Compounds in the Double Annulation Route to Trans-Fused Bicyclic Compounds
Tethered carbon acids bearing nitro groups undergo a double Michael reaction with 3-butyn-2-one, and the cyclic products thereby obtained can be transformed into trans-fused bicyclic compounds with high levels of substitution and functionality. Three new C−C or C−N bonds, two new rings, two to four new stereocenters, and one or two new quaternary centers are created in this novel double annulation of two acyclic, readily available starting materials. Examples of the synthesis of trans-decalins, trans-hydrindanes, and trans-perhydroindoles are presented. Methods for converting the nitro groups in the double Michael and double annulation products into other groups are also described.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.