lessphp import path issue, if I use manual import path

I am working on lessphp compiler for my own development needs, here is what I am trying to achieve.

a) I have parent theme and child theme both have less files.

b) Using twitter bootstrap less files

c) Parent theme have twitter bootstrap less files

d) I am trying to use less files from parent theme in my child theme less file by using @import

I have tried:
a) Passing paths as php variables by using lessphp setVariables(), and it gives me something like this.

i) @import “E:wamppersonalmultisite/wp-content/themes/my-theme/bootstrap/variables.less”;

ii) @import “E:wamppersonalmultisite/wp-content/themes/my-theme/bootstrap/mixins.less”;

code used:

@import "@{template_directory_path}/bootstrap/mixins.less"; 
@import "@{template_directory_path}/bootstrap/variables.less";

but its outputed as is in .css file instead of being imported as less file for parsing.

b) I tried to set directory search paths using lessphp addImportDir(), but it didn’t worked either,

so anybody familiar with my situation, wanna help me out?