A Concise and General Method for Doubly Attaching 2‐Ketosugars to Aglycon Diols: Synthesis of the Gomphosides and Spectinomycin

Stereochemical study of iminodihydrofurans based on experimental measurements and SOPPA calculations of 13C13C spin–spin coupling constants

“…in ascorbic, 1 penicillic, tetronic acids and their thiol analogs, 2 anti-AIDS drugs, such as d4T [1-(2 0 , 3 0 -dideoxy--Dglyceropent-2-enofuranosyl)thymine] and AZT f1- [4-azido-5-(hydroxymethyl)tetrahydrofuran-2-yl]-5-methylpyrimidine-2,4-(1H, 3H)-dioneg. 3 The dihydrofuran structure occurs in cardenolides 4 (cardioactive steroid lactones), dysidiolide 5 -the only known natural inhibitor of a protein phosphatase cdc25A -as well as in a great variety of other natural molecules like sesquiterpenes, 6 pulvinic acid derivatives, 7 etc. As an example of the dihydrofurans' biological activity in strigol and its analogs, the dihydrofuranone parts are primarily responsible for the germination of seeds.…”

“…The same is true for 2 and 3, which follows from their experimental values of 1 J(C-3,C-4) and 1 J(C-4,C-5) couplings (Table 1). The changes of [1][2][3][4]CO) in different conformations of 1(Z) are less pronounced (Table 3); however, they are quite predictable (as arising from the different s-characters of the C 4 -CO bond in s-cis and s-trans conformers with enhanced -conjugation in the latter). One more interesting trend that could be traced out in the experimental values of 1 J(C-3,H) CONCLUSIONS Experimental measurements and high-level ab initio calculations of 13 C-13 C spin-spin coupling constants in the series of iminodihydrofurans revealed that title compounds formed and existed in solution as the individual Z isomers adopting orthogonal orientation of the amino, alkylamino and dialkylamino groups and the s-trans orientation of the CONH 2 group at the C 4 position of the 2,5-dihydro-2-iminofuran moiety.…”

Synthesis of Analogues of (+)-Gomphoside, a Potent HIF-1 Inhibitor and Cardenolide

“…Lichtenthaler et al developed a practical method for the bisacetalic annulation of 2-ketosugars to glycol [14], 1,2-cycohexane diols [15], cholestanediol [16], and gomphogenin, which led to the successful synthesis of the natural products (+)-gomphoside 1, (-)-3ꞌ-dehydrogomphoside 3a and (+)-3ꞌ-epi-gomphoside 3b [17].…”

Organocatalytic Enantioselective Synthesis of 1,4‐Dioxanes and Other Oxa‐Heterocycles by Oxetane Desymmetrization

“…This mild process proceeds with exceedingly high efficiency and enantioselectivity to establish the quaternary stereocenters. [1][2][3] Asymmetric catalysis has not been well exploited to date, [4] particularly for general 1,4-dioxanes (functionalized but not restricted to certain bicyclicf rameworks). [1] Fore xample,t he compounds I, II,a nd III exhibit impressive antiviral, anticancer, and cardiotonic activities,r espectively ( Figure 1).…”

“…[1] Fore xample,t he compounds I, II,a nd III exhibit impressive antiviral, anticancer, and cardiotonic activities,r espectively ( Figure 1). [1][2][3] Asymmetric catalysis has not been well exploited to date, [4] particularly for general 1,4-dioxanes (functionalized but not restricted to certain bicyclicf rameworks). [2] Despite their proven versatility,e fficient asymmetric assembly of chiral 1,4-dioxanes has remained underdeveloped, and currently relies largely on the traditional strategies employing chiral starting materials.…”