A New Nucleophilic Addition/Ring-Closure Sequence. Enantioselective Synthesis of 3-Deoxy-8-oxatropanes

Abstract

[reaction: see text] A study of new nucleophilic addition/ring-closure (NARC) sequences has resulted in the development of a stereoselective synthetic route to 3-deoxy-8-oxatropanes. The new sequences consisted of either a syn or anti aldol addition, employing an omega-alkenoyl sultam, followed by two-step bicyclic ring construction involving, consecutively, ring-closing metathesis and intramolecular oxymercuration.

Recent advances in the application of the Oppolzer camphorsultam as a chiral auxiliary

“…123 Perlmutter et al determined that Et 2 BOTf improves the anti-selective aldol addition using an Oppolzer sultam in the synthesis of (+)-nonactic acid 124 and oxatropanes. 125 An excess of diethylboron triflate in the aldol additions using Oppolzer sultam to both aliphatic and aromatic aldehydes resulted in high anti diastereoselectivity (up to 98:2). It should be noted that an excess of Et 2 BOTf is essential to advance and impose the anti-selective aldol addition.…”

Efficient synthesis of 8-oxa-bicyclo[3.2.1]octane derivatives from d-arabinose

“…1 Similarly, 8-oxa-bicyclo[3.2.1]octane derivatives have been widely used as key precursors for the synthesis of natural and unnatural products, such as sesquiterpenes (1,5-epoxysalvia-4(14)-ene), 2 diterpenes (Cladiellin), 3 alkaloids (Aspergillin PZ, 2 pyrrolizidine alkaloids 4 ), tropane analogues, 5 and Phamoidride B, 6 which show interesting biological activities. Recently, more attention has been paid to the synthesis of conformationally restricted sugar analogues, because they are likely to be resistant to the action of glycosidases and glycosyl transferases.…”

“…2 Another is to create the cyclic systems by stepwise processes, including SmI 2 -mediated nucleophilic acyl addition 9 and intramolecular oxymercuration. 5 At present, various methods have been used for the conversion of sugars to seven-membered carbocyclic compounds, 10 but the enantioselective synthesis and specific spatial distribution of the hydroxyl groups on the ring are often problematic. In this report, the TIBAL-promoted Claisen rearrangement of allyl vinyl ethers and ring-closing metathesis (RCM) were used to construct the polyhydroxycyclic heptenes.…”

Regioselective Palladium-Catalyzed Formate Reduction of N-Heterocyclic Allylic Acetates

“…However, modification of the resulting endo -olefin is limited by the poor selectivity in discriminating between the two olefinic carbon atoms. For example, hydroboration and oxymercuration of an unsymmetrically disubstituted endo -olefin formed by RCM gave a mixture of regioisomers. , The lack of regioselectivity was also oberved in epoxidation, followed by nucleophilic ring opening of endo -olefins …”