Despite the extensive amount of research on nonenzymatic [1,2]-hydride shifts.2 there have been particularly few reports on similar transfers related to carbohydrates.3 We wish to report here the novel example of the stereoselective [1,2]-hydride shifts which occured in the reactions of methyl 3-0-mesyl-0-allofuranoside derivatives with MeMgI. These reactions will serve to prepare not only specifically labeled sugars but also branched-chain deoxy sugars. Treatment of 1,2:5,6-di-O-cyclohexylidene-a-0-allofuranose4 with mesyl chloride gave the corresponding mesylate 1 [88%; mp 119.5-121.5O; [a]E3 +82.2" (c 1.3, CHC13)]. A suspension of 1 in absolute methanol was gently refluxed in the presence of sulfuric acid for 3 hr. The methanol was removed by repeated coevaporation with dry benzene to give, after neutralization with calcium hydroxide, an anomeric mixture of methyl 5,6-O-cyclohexylidene-3-O-mesyl-B-D-allofuranoside 2p [needles; mp 138-140"; [PIi -44.6" (c 1, CHC13); mass m/e 352 (M+), 141 (the 5,6-0-cyclohexylidene group)] and its cx-anomer ga [prisms; mp 118-119'; [w]i2 +g7.7' (c 1, CHC13); mass m/e 352 (M+), 1411 in a ratio of 2:l. Each anomer could be separated by fractional crystallization from isopropyl ether-benzene. In order to demonstrate the hydride shift, the deuterated (at C-2) analogues of 2a and 3a were prepared. Thus, 3a was oxidized with Ru04, followed by reduction with NaB04 to give exclusively a monodeuterated "0-allo" analogue b [mass m/e 353 (M+); nmr (COC13) 6 4.92 (lH, s, H,)]; the use of Na8H4 instead of NaB04 had resulted in the formation of 3a. Treatment of 3b with refluxing methanol in the presence of 6 4.87 (lH, s, H,)]. An ethereal solution of MeMgI (6 mol. dry ether at O-5' over a period of 40 min, sulfuric acid gave zb [mass m/e 353 (M+); nmr (COC13) equiv.)5 was added to a stirred suspension of ga in and the mixture was stirred at room temperature for