Reactions of ortho esters of myo-inositol 8 or 10 with 1-2 equiv of Grignard reagents in benzene-ether yield regio- and stereoselectively the corresponding ring opening products having a free hydroxy group at C-1. The regioselectivity is rationalized owing to the presence of the 2-methoxy group which will serve as an auxiliary to form a chelation complex 12 with magnesium. Inositol derivatives having two free hydroxy group at C-1 and C-3 positions can be achieved from reactions of 6 or 8 with excess Grignard reagents or under more drastic conditions. The reaction of 8b with excess LiAlH(4)/AlCl(3), on the other hand, yields the corresponding 1,5-diol 19.

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1,4-Di-tert-alkoxy-(2S,3S)-2,3-butanediols 2 were obtained from the reactions of 2S,BS-threitol bisketals with Grignard reagents. The reactions of benzylic acetals 3, prepared from 1,4-di-tertalkoxy-(2S,3S)-2,3-butanediols and aromatic aldehydes, with aryl or secondary or sterically hindered Grignard reagents give the corresponding ring-opening products 4 in high diastereoselectivity.There has been an increasing interest in the stereoselective ring opening of acetals by means of nucleop h i l e~.~-~ Most of these approaches involve the preferential complex formation of acetals with a Lewis acid and subsequent invertive substitution by nucleophiles (Scheme 1).2 The retentive ring cleavage of acetals has been investigated only briefly, mostly related to the reductive ring opening with metalRecently, Yamamoto and his co-workers reported the highly diastereoselective retentive alkylation of chiral acetals using novel organoaluminum reagent^.^ However, only methyl-or primary alkylaluminum reagents can be used. We now wish to describe our investigations on the highly diastereoselective reactions of secondary or sterically bulky Grignard reagents with chiral acetals prepared from aldehydes and tunable chiral diols. Results and DiscussionWe recently reported a chelation-assisted regioselective alkylative cleavage of cyclic ketals with Grignard rea g e n t~.~ By using this strategy, 1,4-di-tert-alkoxy-(2S,3S)-2,3-butanediols 2 were easily accessible from the corresponding L-tartaric acid-based bisketals 1.6 Diols 2 might demonstrate certain unique properties to serve as a ligand in asymmetric reactions. First, the size of the alkoxy substituents can be tuned. Second, the oxygen atom in the alkoxy substituent can act as an additional ligand for complexation with the metallic species which would result in the enhancement of the stereoselectivity of the reaction. Such complexation has been shown to be extremely important to direct the regioselective alkylative ring opening of a~etonides.~ On the basis of this @ Abstract published in Advance ACS Abstracts, November 15,1994. (1) For a recent review, see: Alexakis, A.; Mangeney, P. Mori, A.; Arai, I.; Yamamoto, H. Tetrahedron Lett. 1986, 26, 983. (c) Mori, A.; Fujiwara, J.; Maruoka, K.; Yamamoto, H. J. Organomet. Chem. 1986,285, 83. (d) Mori, A.; Fujiwara, J.; Maruoka, K.; Yamamoto, H. Tetrahedron Lett. 1983,24, 4581.(4) (a) Ishihara, K.; Hanaki, N.; Yamamoto, H. conjecture, we felt that this advantage could be made use of in the diastereoselective ring-opening reactions of chiral acetals 3 with Grignard reagents.

Diastereoselective cyclopropanation of R,β-unsaturated ketones or related compounds has recently received much attention. [2][3][4][5][6][7][8] Chiral ketals of R,β-unsaturated carbonyl compounds (1) are commonly used to furnish diastereoselective Simmons-Smith cyclopropanation (eq 1). 2,3 The

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