163181-96-2Relevant articles and documents
Enantioselective Total Syntheses of the Proposed and Revised Structures of Methoxystemofoline: A Stereochemical Revision
Huang, Su-Yu,Gao, Long-Hui,Huang, Xiong-Zhi,Huang, Pei-Qiang
, p. 11053 - 11071 (2021)
This article describes the full details of our synthetic efforts toward the enantioselective total synthesis of the complex alkaloid methoxystemofoline. The enantioselective construction of the tetracyclic core features: (1) the Keck allylation at the N-α bridgehead carbon to forge the tetrasubstituted stereocenter; (2) an olefin cross-metathesis reaction for the side-chain elongation that is amenable for the synthesis of congeners and analogues; and (3) a regioselective aldol addition reaction with methyl pyruvate that ensured the subsequent regioselective cyclization reaction to construct the fourth ring. Overman's method was employed to install the 5-(alkoxyalky1idene)-3-methyl-tetronate moiety. In the last step, a nonstereoselective reaction resulted in the formation of both the proposed structure of methoxystemofoline and its E-stereoisomer, the natural product (revised structure), in a 1:1 ratio. We suggest to rename the natural product as isomethoxystemofoline, and report for the first time the complete 1H NMR data for this natural product.
Modular and stereoselective synthesis of tetrasubstituted helical alkenes via a palladium-catalyzed domino reaction
Liu, Hongqiang,El-Salfiti, Mohamed,Chai, David I.,Auffret, Jeremy,Lautens, Mark
supporting information; scheme or table, p. 3648 - 3651 (2012/09/08)
A highly modular and stereoselective synthesis of tetrasubstituted helical alkenes is accomplished by a Pd-catalyzed norbornene-mediated domino reaction. This protocol features the rapid assembly of four C-C bonds via sequential C-H activations and carbopalladations along with efficient access to enantiopure bromoalkyl aryl alkyne precursors using homologative alkynylation as the key transformation. Three distinct elements of stereoselectivity were observed in the preparation of the chiral helical alkenes: retention of stereochemistry of the substrates, induced helical diastereoselectivity in the alkene formation, and the exclusive exo-facial selectivity of the norbornene incorporation.
SYNTHESIS OF THE METHYL α-GLYCOSIDE OF THE INTRACATENARY DISACCHARIDE REPEATING UNIT OF THE O-POLYSACCHARIDE OF VIBRIO CHOLERAE O:1. A COMPARISON OF TWO ASSEMBLY STRATEGIES
Gotoh, Makoto,Kovac, Pavol
, p. 1193 - 1214 (2007/10/02)
The two strategies engaged in the construction of the title disaccharide 17 comprise: 1. assembly of a diamino disaccharide and its N-acylation using chiral reagents to introduce the 4-(3-deoxy-L-glycero-tetronyl) group, followed by deprotection, and 2. preparation of a glycosyl acceptor and a glycosyl donor both having the chiral 3-deoxy-L-glycero-tetronamido group already in place, their condensation to give a fully substituted disaccharide, and deprotection.Accordingly, the crystalline diamino disaccharide methyl 2-O-(4-amino-3-O-benzyl-4,6-dideoxy-α-D-mannopyranosyl)-4-amino-3-O-benzyl-4,6-dideoxy-α-D-mannopyranoside, (14), was prepared from the known diazido disaccharide 12, and treated with the lactone 30, or its acetylated or benzylated analogs 31 and 32, respectively, as the N-acylating reagents.Subsequent deprotection of the respective products applying standard chemistry gave 17.Alternatively, the methyl α-glycoside of the monomeric intracatenary repeating unit of Vibrio cholerae O:1 (2) was converted to the fully benzoylated glycosyl chloride 26, and the latter glycosyl donor was condensed with methyl 3-O-benzyl-4,6-dideoxy-4-(2,4-di-O-benzoyl-3-deoxy-L-glycero-tetronamido)-α-D-mannopyranoside (24), to give the corresponding, fully protected derivative 27.Deprotection then readily gave 17.It appears that the title disaccharide can be most efficiently synthesized using synthons 24 and 26.The lactones 30 and 32 appear to be promising acylating reagents for the introduction of the 3-deoxy-L-glycero-tetronamido group when higher oligosaccharides in this series will be synthesized via their (poly)amino precursors.
