Electrophilic Azidation for Stereoselective Synthesis of 2-Azido-2-deoxyaldono-1,5-lactones

A Modular Approach to the Total Synthesis of Tunicamycins

“…Selective oxidation of the primary hydroxy group in 17 was achieved in the presence of TEMPO and BAIB; [26] simultaneous acetal formation led to pyranose 18,w hich, however,i mmediately oxidized to lactone 19 (92 %). Azidolactone 19 readily underwent epimerization (CDCl 3 ,R T) at the C10' position ( Figure S2), [27] and was thus quickly reduced into lactol 18 with DIBAL-H. Subsequent acylation led to tunicamine derivative 20 (90 %over 2steps).…”

Stereoselective Synthesis of 2-Azido-2-deoxy-β-d-mannosides via Cs2CO3-Mediated Anomeric O-Alkylation with Primary Triflates: Synthesis of a Tetrasaccharide Fragment of Micrococcus luteus Teichuronic Acid

“…With all of the 2-azido-2-deoxy- d -mannoses in hand, we set to investigate the anomeric O-alkylation of those lactols with electrophiles (Table ). To our delight, cesium carbonate-mediated anomeric O-alkylation of known 2-azido-2-deoxy-3,4,6-tri- O -benzyl- d -mannose ( 16 ) with known primary triflate 17 under standard conditions ( 16 (1.0 equiv), 17 (2.0 equiv), Cs 2 CO 3 (2.5 equiv), ClCH 2 CH 2 Cl, 40 °C, 24 h) furnished the desired 2-azido-2-deoxy-β- d -mannoside 19 in 81% yield (β only). Under the same reaction conditions, a number of partially or fully protected 2-azido-2-deoxy-β- d -mannoside disaccharides ( 20 – 24 ) were obtained from corresponding lactols and primary triflates ( 17 or 18 ) in good yields and excellent anomeric selectivity.…”

“…Disaccharide 19 was prepared from known lactol donor 16 (47.5 mg, 0.1 mmol) and triflate acceptor 17 (119 mg, 0.2 mmol) following the general procedure. The crude reaction mixture was purified by preparative TLC (hexanes/EtOAc = 2/1) to afford compound 19 (77.3 mg, 81%) as white solid.…”

Preparation and Synthetic Applications of Five-to-Seven-Membered Cyclic α-Diazo Monocarbonyl Compounds

“…Later, it was shown that various α-diazo-γ-butyrolactones can be synthesized in direct diazo transfer conditions at low temperatures. However, this method did not gain popularity because of the formation of large numbers of triazine and azide side-products [ 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 ]. Much better results were achieved using detrifluoroacetylating diazo transfer, which to-date is the most widely accepted method of synthesizing α-diazo lactones, including six- and seven-membered ones ( Scheme 73 ) [ 5 , 96 , 109 , 110 ].…”