Carbasugar Synthesis via Vinylogous Ketal: Total Syntheses of (+)-MK7607, (−)-MK7607, (−)-Gabosine A, (−)-Epoxydine B, (−)-Epoxydine C, <i>epi</i>-(+)-Gabosine E and <i>epi</i>-(+)-MK7607

Carbasugars, the carbocyclic analogues of sugars, constitute an important class of natural products with more than 140 members known and have attracted much attention due to their diverse biological activities like anticancer, antibacterial, herbicidal, and various enzyme inhibitory activities. As many carbohydrates are involved in various cellular signaling pathways, there is great interest in synthesis and biological exploration of carbasugars. Herein, we have developed a methodology to install an α,β-unsaturated aldehyde functionality on different inositols and derivatives by vinylogous elimination of the O-protecting group under mildly acidic condition. We have illustrated the versatility and utility of our methodology by the total syntheses of seven carbasugars viz. (−)-MK7607, (−)-gabosine A, (−)-epoxydine B, (−)-epoxydine C, (+)-MK7607, 1-<i>epi</i>-(+)-MK7607 and 1-<i>epi</i>-(+)-gabosine E

Vinylogy in Orthoester Hydrolysis: Total Syntheses of Cyclophellitol, Valienamine, Gabosine K, Valienone, Gabosine G, 1-<i>epi</i>-Streptol, Streptol, and Uvamalol A

C7-cyclitols represent an important category of natural products possessing a broad spectrum of biological activities. As each member of these compounds is structurally unique, the usual practice is to synthesize them individually from appropriate polyhydroxylated chiral pools. We have observed an unusual vinylogy in acid mediated hydrolysis of enol ethers of <i>myo</i>-inositol 1,3,5-orthoesters giving a synthetically versatile polyhydroxylated cyclohexenal intermediate. We have exploited this unprecedented reaction for developing a general strategy for the rapid and efficient syntheses of several structurally diverse natural products of C7-cyclitol family. We have made an appropriately protected advanced intermediate 25 in five steps from the cheap and commercially available <i>myo</i>-inositol, and this common intermediate has been used to synthesize eight natural products in racemic form. We could synthesize (±)-cyclophellitol in seven steps, (±)-valienamine in five steps, (±)-gabosine I in five steps, (±)-gabosine G in six steps, (±)-gabosine K in three steps, (±)-streptol in six steps, (±)-1-<i>epi</i>-streptol in two steps, and (±)-uvamalol A in five steps from this intermediate

Vinylogy in Orthoester Hydrolysis: Total Syntheses of Cyclophellitol, Valienamine, Gabosine K, Valienone, Gabosine G, 1-<i>epi</i>-Streptol, Streptol, and Uvamalol A

C7-cyclitols represent an important category of natural products possessing a broad spectrum of biological activities. As each member of these compounds is structurally unique, the usual practice is to synthesize them individually from appropriate polyhydroxylated chiral pools. We have observed an unusual vinylogy in acid mediated hydrolysis of enol ethers of <i>myo</i>-inositol 1,3,5-orthoesters giving a synthetically versatile polyhydroxylated cyclohexenal intermediate. We have exploited this unprecedented reaction for developing a general strategy for the rapid and efficient syntheses of several structurally diverse natural products of C7-cyclitol family. We have made an appropriately protected advanced intermediate 25 in five steps from the cheap and commercially available <i>myo</i>-inositol, and this common intermediate has been used to synthesize eight natural products in racemic form. We could synthesize (±)-cyclophellitol in seven steps, (±)-valienamine in five steps, (±)-gabosine I in five steps, (±)-gabosine G in six steps, (±)-gabosine K in three steps, (±)-streptol in six steps, (±)-1-<i>epi</i>-streptol in two steps, and (±)-uvamalol A in five steps from this intermediate