$args  = array(
    'post_status' => 'any',
    'post_type'   => 'any',
    'numberposts' => -1,
    'meta_query'  => array(
        array(
            'key'     => 'Asin_unique',
            'value'   => '(B006MWDNVI,B00BCMCIS2,B01ARRJFGA)',
            'compare' => 'IN',
        )
    )
);

$posts = get_posts( $args );

$args  = array(
    'post_status' => 'any',
    'post_type'   => 'any',
    'numberposts' => -1,
    'meta_query'  => array(
        array(
            'key'     => 'Asin_unique',
            'value'   => array('B006MWDNVI','B00BCMCIS2','B01ARRJFGA'),
            'compare' => 'IN',
        )
    )
);

$posts = get_posts( $args );