A synthesis of the C29-C51 fragment of spongistatin 1, containing the E and F rings, has been completed. The approach relies on four diastereoselective aldol additions and an asymmetric glycolate alkylation to establish eight of the eleven stereogenic centers. The intact chlorodiene side chain was appended by a Lewis acid catalyzed addition of an allylstannane to an epoxy enol ether.

The enantioselective synthesis of novel C-linked spiroacetal-triazoles 10 is reported. The key step involves reaction of acetylenic spiroacetal 11 with several azides by the Copper-Catalysed Azide-Alkyne Cycloaddition (CuAAC). The biologically privileged spiroacetal scaffold 11 was prepared from silyl-protected Weinreb amide 19 using several reliable Grignard additions and a highly diastereosel...

A highly diastereoselective organocatalytic synthesis of unique functionalised vinyl epoxides, displaying a Morita-Baylis-Hillman backbone, has been developed by means of an user friendly sulfonium ylide epoxidation of aldehydes from a readily available alpha-(bromomethyl)acrylamide derivative. The first result in the asymmetric version is discussed.

A highly diastereoselective Ugi reaction involving a chiral cyclic imine, two enantiomerically pure isocyanides and various carboxylic acids was employed for the synthesis of polyfunctionalized pyrrolidines. Both chiral substrates have been efficiently prepared by chemoenzymatic methodologies from readily available achiral substrates. This highly convergent approach can find an application in t...

NHC-catalyzed annulation of enals with 2-enoylpyridines or 2-enoylpyridine N-oxides leading to the diastereoselective synthesis of β-lactone-fused cyclopentanes is reported. The reaction proceeds via the generation of homoenolate equivalent intermediates and tolerates a broad range of functional groups.

A concise, diastereoselective total synthesis of (±)-cortistatin J has been completed in 20 steps from furan. Key steps include an intramolecular [4 + 3] cyclization of a disubstituted furan with a (Z)-2-(trialkylsilyloxy)-2-enal to construct the tetracyclic core and a (Z)-vinylsilane/iminium ion cyclization to form the A ring.

Tetrahydroxanthenones, which can be easily prepared by a domino oxa-Michael aldol condensation, offer various possibilities for diastereoselective functionalization, giving access to the stereocontrolled synthesis of stereochemical triades or tetrades, which represent privileged structural motifs. In most cases, the relative stereochemistry was unequivocally established by crystal structure ana...

An efficient approach toward the synthesis of the 6,6,5,7-tetracyclic core of the daphnilongeranin B, a Daphniphyllum alkaloid, is reported. The bridged 6,6-bicyclic system was constructed using a gold(i) catalysed Conia-ene reaction, while the 5- and 7-membered rings were assembled by two diastereoselective Michael addition reactions, respectively.

An efficient high yielding improved method for the enantio- and diastereoselective cyclopropanation of chiral epoxides using triethylphosphonoacetate and base (Wadsworth-Emmons cyclopropanation) is reported. The utility of this protocol is illustrated by concise and practical synthesis of cascarillic acid, grenadamide and L-(-)-CCG-II, a cyclopropane containing natural products.

A concise synthetic strategy has been developed for the synthesis of the macrolactone core 2 of a unique polyketide callyspongiolide 1. The key features of the strategy included an Evan's asymmetric alkylation, diastereoselective Michael type alkylation, Brown's asymmetric allylation reaction, an allylic alkylation of an activated Z-allylic alcohol and an intramolecular Z-selective intramolecul...