N-benzoylcarbamate cyclizations

The tethered nitrogen in natural products synthesis

“…Our candidate for the tethered nitrogen nucleophile for intramolecular 'S N 2' is the anion of an N-benzoylcarbamate, prepared simply by reaction of benzoyl isocyanate with an appropriately positioned hydroxy (Scheme 10). 20,21 Because the reaction with benzoyl isocyanate occurs rapidly under mild and neutral conditions, sensitive substrates such as epoxy alcohols and diol monotriflates can be used, and many of these are available in enantiomerically pure form. As a model, cinnamyl alcohol 62 was converted to its N-benzoylcarbamate derivative, epoxidized, and then treated with sodium hydride to generated the sodium salt of the N-benzoylcarbamate anion, 64.…”

“…[23][24][25][26][27][28][29] Pyranoside substrates can also be used for a direct sugar-toaminosugar transformation (Scheme 11). 20,21 Thus methyl 4,6-O-benzylidene-a-d-glucopyranoside 67, a trans-vicinal diol, was selectively converted to its 2-O-trifluoromethanesulfonate ester by reaction with triflic anhydride. Monotriflation of diols under these conditions tends to occur preferentially at the hydroxy flanked by a cis,vicinal heteroatom, here the methoxy oxygen, presumably because of intramolecular H-bonding and an accompanying increase in the electron density at the hydroxy oxygen.…”

The synthetic methodology of nonracemic glycidol and related 2,3-epoxy alcohols

“…In the cases of sulcatol (83) and ramulosin (84), the second "nucleophilic" addition was actually reduction. The initial organometallic additions are described in Scheme 20 and Table 10 (entry 1, ref 155), respectively.…”

Total Synthesis of (+)-Lactacystin

“…Several meritorious approaches have been reported previously, although they either lack generality (i.e., yield only one of the four possible diastereomers) or required the preparation of a scalemic catalyst . We developed a simple, concise strategy employing commercially available materials, exploiting a catalytic Sharpless epoxidation, benzyl isocyanate-induced epoxide opening, and epimerization of an oxazolidinone ester …”