Methyl d-arabino-hex-2-ulopyranosonate as a building block for spiro[1,4-benzoxazine-2,2′-pyrans]

Synthesis and X-ray Crystal Structures of Novel Spiro 1,3-benzoxazine Dimers

“…To the best of our knowledge, there has been no previous report on the synthesis of spiro 1,3-benzoxazine dimers; all previous reports describe the synthesis of spiro compounds which combine benzoxazines with other heterocyclic systems. [1][2][3][4][5][6] Recently we have been able to obtain spiro-quinazoline dimers from the reaction of 2-aminoacetophenone hydrazones with triphosgene. 13 Hydrazones of 2-hydroxyacetophenone which carry a chlorine or bromine substituent gave 1,3benzoxazines upon treatment with triphosgene.…”

Glucopyranosylidene-spiro-benzo[b][1,4]oxazinones and -benzo[b][1,4]thiazinones: Synthesis and Investigation of Their Effects on Glycogen Phosphorylase and Plant Growth Inhibition

“…For the preparation of the target compounds, a literature method was planned to be adapted to serve as the starting point . Thus, in the first step, a 2-nitrophenyl glycoside of a methyl ulopyranosonate was prepared followed by a reduction and cyclization step to obtain the spirocycle.…”

“…For the synthesis of a spirocyclic analogue of DIBOA-Glc ( J ), the partial reduction of 2a was investigated (Table ). Using zinc dust and NH 4 Cl in methanol resulted in the hydroxamic acid 7 together with lactam 4a in low overall yield. Reduction with NaBH 4 and hydrogenation over poisoned Pd­(C) afforded exclusively 7 ; the latter method resulted in a slightly higher yield.…”

“…For the preparation of the target compounds, a literature method was planned to be adapted to serve as the starting point. 26 Thus, in the first step, a 2-nitrophenyl glycoside of a methyl ulopyranosonate was prepared followed by a reduction and cyclization step to obtain the spirocycle. By applying the literature conditions to 1 in the presence of 2nitrophenol and K 2 CO 3 in acetone at different temperatures (Table 3, entries 1 and 2), a significant amount of glycal 3 was formed by HBr elimination.…”

“…Anomeric spiroketals of pyranoid sugar derivatives in which additional heteroatoms, especially nitrogen, can be found in a six-membered ring are scarcely known. Syntheses of glycopyranosylidene spiro derivatives of 1,2-oxazines, 1,3-oxazinones, 1,4-oxazines, 1,4-oxazinones, − and 1,4-thiazinones have been reported; however, their biological activity is practically unexplored so far. Only weak glycosidase inhibition and cytotoxicity for some 1,3-oxazinone derivatives have been reported …”