2-methyl-1,2-diols

Methyl-1,2-diols do not pose the problem of the selective monoacylation of the previous 1,2-diols, since in that structure botii a primary group and a less accessible tertiary hydroxy group are present. In face, as shown in Scheme 55, a few 2-methyl-1,2-diols are successfully resolved by the enzymatic transesterification process with high enantioselec-tivity [243]. 

Run no. pH Conv. (mol%) Styrene oxide Methylated diol Diol Benzaldehyde Phenyl acetaldehyde Others... 

All these results are consistent with the 8-lactam structures CCCXCVI and CCCXCVII which received confirmation by conversion of the amino alcohol CCCC to CCCCIII and unambiguous synthesis of the latter from CCCXCVIII. The monotosylate of the methylated diol CCCCI was subjected to reduction with lithium aluminum hydride to give the base CCCCIII. Reaction of the amino alcohol CCCXCVIII with methyl... 

It has been found that aldehydes of the cinnamaldehyde type undergo an interesting biotransformation in the medium of growing baker s yeast yielding optically active methyl diols (e.g., 58, 59). 

In 2003, Schaus and coworkers utilized Binol-derived hydrogen-bond donors 6a and 6b along with triethylphosphine in the enantioselective Morita-Baylis-Hillman reaction of cyclohexenone with various aldehydes (Scheme 10.8) [67]. Control experiments showed that the use of mono-methylated diols resulted in significant decreases in both the yields and enantioselectivities. 

The benzylidene derivative above is used, if both hydroxyl groups on C-2 and C-3 are needed in synthesis. This r/vzns-2,3-diol can be converted to the sterically more hindered a-cpoxide by tosylation of both hydroxy groups and subsequent treatment with base (N.R. Williams, 1970 J.G. Buchanan, 1976). An oxide anion is formed and displaces the sulfonyloxy group by a rearside attack. The oxirane may then be re-opened with nucleophiles, e.g. methyl lithium, and the less hindered carbon atom will react selectively. In the following sequence starting with an a-glucoside only the 2-methyl-2-deoxyaltrose is obtained (S. Hanessian, 1977). 

The 7, i5-unsaturated alcohol 99 is cyclized to 2-vinyl-5-phenyltetrahydro-furan (100) by exo cyclization in aqueous alcohol[124]. On the other hand, the dihydropyran 101 is formed by endo cyclization from a 7, (5-unsaturated alcohol substituted by two methyl groups at the i5-position. The direction of elimination of /3-hydrogen to give either enol ethers or allylic ethers can be controlled by using DMSO as a solvent and utilized in the synthesis of the tetronomycin precursor 102[125], The oxidation of the optically active 3-alkene-l,2-diol 103 affords the 2,5-dihydrofuran 104 in high ee. It should be noted that /3-OH is eliminated rather than /3-H at the end of the reac-tion[126]. 

The carbonylation of 2-methyl-3-butyn-2-oI (50) in benzene gives teraconic anhydride (51). Fulgide (53) (a dimethylenesuccinic anhydride derivative), which is a photochromic compound, can be prepared by the carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (52)[21], The reaction proceeds under milder conditions when PdlOAc) is used as a catalyst in the presence of iodine [23],... 

An early attempt to hydroformylate butenediol using a cobalt carbonyl catalyst gave tetrahydro-2-furanmethanol (95), presumably by aHybc rearrangement to 3-butene-l,2-diol before hydroformylation. Later, hydroformylation of butenediol diacetate with a rhodium complex as catalyst gave the acetate of 3-formyl-3-buten-l-ol (96). Hydrogenation in such a system gave 2-methyl-1,4-butanediol (97). 

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