# What is the stereochemistry resulting from hydroboration of 1-methylcyclopentene?

What is the major product of the following reaction sequence?

I'm supposed to work out the structures of both 2 and 3, but I already know 2 to be 1-methylcyclopentene (as the most substituted alkene is formed during elimination).

For the hydroboration step, boron should add to the less substituted carbon (in an anti-Markovnikov fashion). However, I'm not sure which of the two choices B and C is correct. Why should one diastereomer be formed preferentially over the other?

The final step, the oxidation by hydrogen peroxide, is stereospecific with retention. So the newly-formed $$\ce{C-O}$$ bond is on the same side as the former $$\ce{C-B}$$ bond. Thus, an anti relationship is established between the methyl group and the hydroxy group.
Since 1-methylcyclopentene is planar, a racemic mixture of enantionmers is formed; neither re nor si side are favoured. The scheme below shows the attack from the si side of the $$\mathrm{C2}$$ atom.