Synthesis of (±)-Emtricitabine and (±)-Lamivudine by Chlorotrimethylsilane–Sodium Iodide-Promoted Vorbrüggen Glycosylation
作者:Sarah Jane Mear、Long V. Nguyen、Ashley J. Rochford、Timothy F. Jamison
DOI:10.1021/acs.joc.1c02772
日期:2022.3.4
By simple combination of water and sodiumiodide (NaI) with chlorotrimethylsilane (TMSCl), promotion of a Vorbrüggen glycosylation en route to essential HIV drugs emtricitabine (FTC) and lamivudine (3TC) is achieved. TMSCl–NaI in wet solvent (0.1 M water) activates a 1,3-oxathiolanyl acetate donor for N-glycosylation of silylated cytosine derivatives, leading to cis-oxathiolane products with up to
Halide-Terminated <i>N</i>-Acyliminium Ion−Alkyne Cyclizations: A New Construction of Carbacephem Antibiotics
作者:Eric Metais、Larry E. Overman、Maria Inés Rodriguez、Brian A. Stearns
DOI:10.1021/jo971433w
日期:1997.12.1
A series of 4-(3-alkynyl)azetidinones 13 was prepared from 4-(phenylsulfonyl)azetidine-2-one (9) and isopropyl glyoxylate hydrate. The 3-pentynyl (13a) and 4-phenyl-3-butynyl (13b) azetidinone acetates underwent 6-exo cyclization when treated with 3 equiv of SnCl4 at 0 degrees C to provide 3-(1-chloroalkylidene)carbacephems 15a (65%) and 15b (33%) respectively. In contrast, the 5-butynyl (13d) and 4-(trimethylsilyl)-3-butynyl (13c) azetidinone acetates under ent 7-endo cyclization under similar conditions to give 1-azabicyclo[5.2.0]nonenes 14a (11%) and 14b (71%), respectively. Beginning with penicillin degradation product 18, the more elaborate 3-pentynyl azetidinone cyclization substrate 27 was prepared in seven steps. Exposure to 27 to 3 equiv of SnCl4 in CH2Cl2 at 0 degrees C for 6 h, followed by allowing the reaction mixture to warm to rt, provided the desired 3-(1-chloroethylidene)carbacephem 28 in 60% yield and high (>99%) enantiometric purity. Cleavage of the chloroethylidene group of 28 with ozone gave 3-hydroxy carbacephem 29 in 77% yield. Since this intermediate has been converted in three steps to loracarbef (3), a new formal total synthesis of this carbacephem antiboitic was concluded.
Rhodium-catalyzed reactions of arylbismuth and aryllead reagents with a chiral glyoxylate hydrate in air and water: water-promoted diastereoselectivity enhancement
作者:Rui Ding、Cheng-Sheng Ge、Yong-Jun Chen、Dong Wang、Chao-Jun Li
DOI:10.1016/s0040-4039(02)01814-2
日期:2002.10
In the presence of a rhodium catalyst, a chiral glyoxylate hydrate reacts with arylbismuth and aryllead reagents in water and under an atmosphere of air to give the corresponding addition products in high yields. The diastereoselectivities of the reactions were dramatically improved by using water as the solvent. (C) 2002 Elsevier Science Ltd. All rights reserved.