Не могу правильно сформировать конфиг nginx

у меня есть такой конфиг для сайта

server {
    listen      100.100.100.100;
    server_name site.com www.site.com;
    set $base_root /home/admin/web/site.com/public_html;
    root $base_root;
    index       index.php index.html index.htm;
    access_log  /var/log/nginx/domains/site.com.log combined;
    access_log  /var/log/nginx/domains/site.com.bytes bytes;
    error_log   /var/log/nginx/domains/site.com.error.log error;

    ssl         on;
    ssl_certificate      /home/admin/conf/web/ssl.site.com.pem;
    ssl_certificate_key  /home/admin/conf/web/ssl.site.com.key;

    location / {
        root $base_root/frontend/web;
        index index.php index.html;
        try_files $uri $uri/ /frontend/web/index.php$is_args$args;
        location ~* ^.+\.(jpeg|jpg|png|gif|bmp|ico|svg|css|js)$ {
            expires     max;
        }
    }

    location /admin {
        alias $base_root/backend/web/;

        try_files $uri /backend/web/index.php$is_args$args;

        location ~ ^/admin/assets/.+\.php(/|$) {
            deny all;
        }
    }

    location ~ ^/.+\.php(/|$) {
        rewrite (?!^/((frontend|backend)/web|admin))^ /frontend/web$uri break;
        rewrite (?!^/backend/web)^/admin(/.+)$ /backend/web$1 break;
        fastcgi_param SCRIPT_FILENAME $request_filename;
            if (!-f $request_filename) {
                return  500;
            }

            fastcgi_pass    127.0.0.1:9001;
            fastcgi_index   index.php;
            include         /etc/nginx/fastcgi_params;
    }

    location ~ /\. {
        deny all;
    }

    error_page  403 /error/404.html;
    error_page  404 /error/404.html;
    error_page  500 502 503 504 /error/50x.html;

    location /error/ {
        alias   /home/admin/web/site.com/document_errors/;
    }

    location ~* "/\.(htaccess|htpasswd)$" {
        deny    all;
        return  404;
    }

    location /vstats/ {
        alias   /home/admin/web/site.com/stats/;
        include /home/admin/conf/web/site.com.auth*;
    }

    include     /etc/nginx/conf.d/phpmyadmin.inc*;
    include     /etc/nginx/conf.d/phppgadmin.inc*;
    include     /etc/nginx/conf.d/webmail.inc*;

    include     /home/admin/conf/web/snginx.site.com.conf*;
}

Сам сайт написан на yii2 advanced. Все хорошо работает. Но стала задача создать api в проекте. Я сделал папку api и хочу сделать, что бы запросы /api смотрели в нее. Сделал по принципу /admin

server {
    listen      100.100.100.100;
    server_name site.com www.site.com;
    set $base_root /home/admin/web/site.com/public_html;
    root $base_root;
    index       index.php index.html index.htm;
    access_log  /var/log/nginx/domains/site.com.log combined;
    access_log  /var/log/nginx/domains/site.com.bytes bytes;
    error_log   /var/log/nginx/domains/site.com.error.log error;

    ssl         on;
    ssl_certificate      /home/admin/conf/web/ssl.site.com.pem;
    ssl_certificate_key  /home/admin/conf/web/ssl.site.com.key;

    location / {
        root $base_root/frontend/web;
        index index.php index.html;
        try_files $uri $uri/ /frontend/web/index.php$is_args$args;
        location ~* ^.+\.(jpeg|jpg|png|gif|bmp|ico|svg|css|js)$ {
            expires     max;
        }
    }

    location /admin {
        alias $base_root/backend/web/;

        try_files $uri /backend/web/index.php$is_args$args;

        location ~ ^/admin/assets/.+\.php(/|$) {
            deny all;
        }
    }

    location /api {
        alias $base_root/api/web/;

        try_files $uri /api/web/index.php$is_args$args;

        location ~ ^/api/assets/.+\.php(/|$) {
            deny all;
        }
    }

    location ~ ^/.+\.php(/|$) {
        rewrite (?!^/((frontend|backend)/web|admin))^ /frontend/web$uri break;
        rewrite (?!^/backend/web)^/admin(/.+)$ /backend/web$1 break;
        fastcgi_param SCRIPT_FILENAME $request_filename;
            if (!-f $request_filename) {
                return  500;
            }

            fastcgi_pass    127.0.0.1:9001;
            fastcgi_index   index.php;
            include         /etc/nginx/fastcgi_params;
    }

    location ~ /\. {
        deny all;
    }

    error_page  403 /error/404.html;
    error_page  404 /error/404.html;
    error_page  500 502 503 504 /error/50x.html;

    location /error/ {
        alias   /home/admin/web/site.com/document_errors/;
    }

    location ~* "/\.(htaccess|htpasswd)$" {
        deny    all;
        return  404;
    }

    location /vstats/ {
        alias   /home/admin/web/site.com/stats/;
        include /home/admin/conf/web/site.com.auth*;
    }

    include     /etc/nginx/conf.d/phpmyadmin.inc*;
    include     /etc/nginx/conf.d/phppgadmin.inc*;
    include     /etc/nginx/conf.d/webmail.inc*;

    include     /home/admin/conf/web/snginx.site.com.conf*;
}

Но так не работает. Ошибка

[error] 26703#26703: *1 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 185.183.15.19, server: site.com, request: "GET /api HTTP/1.1", upstream: "fastcgi://127.0.0.1:9001"

Помогите разобраться.

P.S. Ответы "сделай разные поддомены" просьба не писать, так как основной сайт - это и есть поддомен