Synthesis of alkynes and alkynyl iodides bearing a protected amino alcohol moiety as functionalized amino acids precursors

Recent Advances in the Chemical Synthesis of C-Glycosides

“… − Exposure of vinyl oxiranes 176 and 177 to organolithium reagents generated 1,4- cis - C -glycosides 182 – 185 in high yields with excellent anomeric selectivities. , Yb­(OTf) 3 -mediated glycosylation of glycals 143 and 147 with alkylaluminums gave C -glycosides 186 – 188 in good yields albeit in poor diastereoselectivities . Addition of organozinc reagents to glycals 178 , 179 , and 181 was reported to afford α- C -glycosides 189 – 191 in good yields. , Treatment of glucal 143 with potassium alkynyltrifluoroborates using BF 3 ·OEt 2 as the promoter afforded alkynyl glycosides 165 , 192 and 193 in 66–89% yields favoring the α-anomers (from α/β = 93:7 to α only). , Indium-mediated Ferrier-type coupling of glycals 143 and 146 with 1-iodo-2-phenylacetylene was reported to give C -alkynyl glycosides 165 , 194 , and 195 with high α-selectivities. − TMSOTf-catalyzed glycosylation of glucal 143 and l -rhamnal 149 with unactivated alkynes provided alkynyl glycosides 165 , 192 , and 196 in moderate to good yields with excellent α-selectivities. − Zinc-, copper-, and gold-mediated reactions of unactivated alkynes with glycals 143 , 145 , 146 , and 149 proceeded smoothly to provide α- C -alkynyl glycosides 165 and 195 – 199 in a highly stereoselective fashion. − Under the catalysis of InCl 3 , coupling of glucal 143 with heteroaromatic compounds such as 2-benzyloxymethylfuran, thiophene, and N - tert -butoxycarbonyl- ( N -Boc-) protected indole led to C -glycosides 200 – 202 in 68–90% yields with high β-selectivities . Decarboxylative glycosylation of glycals 143 and 146 with β-keto acids using FeCl 3 as the catalyst provided β-keto-functionalized C -glycosides 154 , 203 , and 204 in 36–80% yields with varied anomeric selectivities (from α/β = 5:3 to α only). , Reaction of 143 and 146 with unactivated aryl methyl ketones under the catalysis of tert -butyldimethylsilyl triflate (TBSOTf) in the presence of i PrNEt led to α- C -glycosides 154 , 203 , and 205 in moderate yields .…”

Enantioselective synthesis of indole‐based unnaturalβ‐Alkynylα‐amino acid derivatives via chiral phosphoric acid catalysis

“…18,19 In addition, adding an alkyne moiety to an unnatural amino acid is critical for altering protein activities, which has a significant impact on protein engineering. 20 The major unnatural amino acids with this scaffold [21][22][23] such as propargylglycine (1), p-propargyloxyphenylalanine (2), and p-ethynylphenylalanine (3) are shown in Figure 1.…”