HONG KONG -- Chinese online grocery startups Missfresh and Dingdong Maicai are headed to Wall Street to boost their firepower to fend off big tech rivals in an intensifying battle over the country's vast fresh produce market. Both companies filed applications for initial public offerings in the U.S. earlier this month, racing to become the sector's first listed Chinese company. Dingdong aims to raise up to $357 million at a valuation of about $6 billion, according to its prospectus.