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 myo-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 myo-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-epi-streptol in two steps, and (±)-uvamalol A in five steps from this intermediate.

Natural carbasugars are an important class of biologically active compounds. Due to their conformational freedom and the subtle difference in spectral characteristics between isomers, often their NMR-based structural assignments are erroneous. It is thus important to validate their structural identity through chemical synthesis. We report the first total syntheses and structural validation of five natural carbasugars, namely, lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K in their racemic forms, from a myo-inositol-derived common intermediate. This intermediate was synthesized by the vinylogous ring opening of myo-inositol orthoester cage under mild acidic conditions in six steps from myo-inositol. From this intermediate, we achieved the syntheses of (±)-lincitol A in six steps, (±)-lincitol B in seven steps, (±)-uvacalol I in five steps, (±)-uvacalol J in five steps, and (±)-uvacalol K in seven steps. The structure and relative stereochemistry of these natural products were confirmed by comparing the (1)H and (13)C NMR spectra of synthesised natural products with the reported data. These syntheses involved several unprecedented protecting-group manipulations and unexpected reactivities.

A general strategy for the diverse synthesis of ten disaccharide aminoglycosides, including natural 2‐trehalosamine (1), 3‐trehalosamine (2), 4‐trehalosamine (3), and neotrehalosyl 3,3′‐diamine (8) and synthetic aminoglycosides 4–7, 9, and 10, has been developed. The aminoglycoside compounds feature different anomeric configurations and numbers of amino groups. The key step for the synthesis was the glycosylation coupling of a stereodirecting donor with a configuration‐stable TMS glycoside acceptor. Either the donor or acceptor could be substituted with an azido group. The aminoglycosides prepared in the present study were characterized by 1D and 2D NMR spectroscopy.

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-epi-(+)-MK7607 and 1-epi-(+)-gabosine E.

Herein, we report the total synthesis of landomycins Q and R as well as the aglycone core, namely anhydrolandomycinone and a related core analogue.