1,2-O-Silyl Group Rearrangements in Carbohydrates - Convenient Synthesis of Important Lactose Building Blocks1

Abstract

Base dependent (1a→2a)-O- and (2a→1a)-O-silyl group rearrangements have been observed in lactose. These transformations can be employed for convenient regioselective protection or deprotection at the 2a-O-position. Thus, from readily available 6 with NaH and Bn-Br in DMF 2-O-TDS-protected benzyl lactoside 7β is directly accessible in high yield. 7β can be easily converted into 2a-O-unprotected, 2a-O-pivaloyl-protected, and 4b-O-unprotected lactose derivatives 8, 9, and 2, respectively.