Boulter was among the British hopes to fall at the first hurdle on day two as she lost 6-2 6-4 to Italian teenager Tyra Caterina Grant.
It is the first time since 2017 that Boulter has lost in the opening round at Wimbledon in what is her first loss to a qualifier at a Grand Slam tournament.
It comes just 18 days after she achieved the biggest win of her career by ranking, when she defeated world number two Elena Rybakina in a stunning performance at Queen's.
Seeking to push back against unwanted British history on court three, Boulter got off to the worst possible start as the 18-year-old Grant, who had never contested a singles match on grass at any level prior to Wimbledon qualifying this year, went an early break up.
Boulter could not respond as the opening set slipped away and she was unable to recover from another setback early in the second.
The Briton did not force a single break point in the match, with Grant, making her Grand Slam main-draw debut, dropping just three points across her final four service games as she comfortably served out victory.
Last year, 13 British players went out in round one. Not since 1994 have as many as 14 fallen at the first hurdle.
Pinnington Jones played just five games after returning to complete his match against American 28th seed Brandon Nakashima, losing 6-3 7-6 (7-5) 7-5 after trailing 4-3 in the third set when play was suspended late on Monday.
Wendelken, ranked 202nd in the world, took the first set against French world number 75 Valentin Royer but eventually lost 4-6 6-3 6-3 6-3.
Nine British players are in action in total on Tuesday, with Eastbourne semi-finalist Toby Samuel still to face 15th seed Jakub Mensik.
British number two Jan Choinski will take on Vit Kopriva, while Billy Harris is up against 19th seed Karen Khachanov.