Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Construction of the B ring. Reagents and conditions. a) Boc2O, 4‐(dimethylamino)pyridine (DMAP), MeCN, reflux, 57.5 h, 72 %; b) 1) NaBH4, EtOH, 25 °C, 3 h; 2) TFA, CH2Cl2, 25 °C, 1.5 h, 73 % (two steps); c) 1‐allyl 3‐ethyl 2,2‐dihydroxymalonate, TFA, AcOH, 25 °C, 6 h, 80 %; d) BnBr, K2CO3, acetone, 25 °C, 8 h, 83 %; e) 1) Swern oxidation; 2) aq KCN, AcOH, THF, 25 °C, 2 h, 56 % (two steps); f) 1) Pd(PPh3)4, dimedone, THF, 25 °C, 1 h; 2) CHCl3, reflux, 2 h, 72 % (two steps).
