A short and simple synthesis of the antitumor agent etoposide

Novel “Reverse Kahne-Type Glycosylation”: Access to O-, N-, and C-Linked Epipodophyllotoxin Conjugates

“…Though Koenigs−Knorr glycosylation was originally used to make podophyllotoxin conjugates, , most current approaches rely upon a “reverse glycosylation” approach due to Kuhn and von Wartburg, wherein the aglycon serves as the “reverse glycosyl donor” and the sugar as “reverse glycosyl acceptor.” The reaction is normally run at −20 to 0 °C, under F 3 B−Et 2 O promotion. An important modification by Allevi, wherein a silyl sugar is employed, facilitates control of the anomeric stereochemistry …”

The Synthesis and Glycoside Formation of Polyfluorinated Carbohydrates

“…With a free OH-6 group, such as in 1207 (Scheme C), the reaction also worked well, with 1208 obtained in 76% yield, although the OH-6 group was partially allylated leading to 1209 in 23% yield. An interesting result was obtained with a known direct glycosidation , using a strong Lewis acid (Scheme D): reaction of 1205 with the podophyllotoxin derivative 1210 gave 1211 in good yield. This glycosidation was thought to proceed via the benzylic cation 1212 and, while the anomeric selectivity was relatively modest, complete facial selectivity for the reaction with 1212 was reported …”

The chemical synthesis of aryltetralin glycosides

“…The synthetic potential of this protocol was further demonstrated by the work from Macdonald's group (Scheme 20). 49 Thus, inverted glycosylation between 117 and 121 afforded glycoside 122 under the promotion of 3.0 equivalents of BF 3 •Et 2 O (75%). It should be noted that the low concentration (80 mL mmol −1 ) of the substrates in CH 2 Cl 2 is a guarantee to get satisfactory glycosylation yield and there was no need to protect the 4′-phenolic OH as well.…”