Syme, winner of the Australian Amateur Championship earlier in the year, beat his Scotland foursomes partner Craig Howie by two holes in the best of the last-eight ties in the Granite City.
“I’m delighted to have won that one as it was always going to be a tough game,” admitted Drumoig man Syme after closing the door with a superb 7-iron to 15 feet behind the hole at the last.
Syme, who helped Great Britain & Ireland retain the St Andrews Trophy in Kent last week, birdied the second, sixth and ninth to be three up at the turn.
Peebles player Howie then reduced the deficit with a birdie-3 at the 10th before both players made 4s at the long 12th.
Syme’s “only bad shot of the day” allowed former Stirling University scholar Howie to get back to just one down but Syme held on to set up a last-four clash with fellow 21-year-old Andrew Burgess from Nairn.
Burgess booked his place in the semi-finals with a 2&1 victory over Forres player Jeff Wright, who finished third in the Scottish Order of Merit last season.
“It was a different wind today than what we’ve been used to this week and, as a result of that, it was a bit scrappy for the first seven holes,” said Burgess.
“But I started to hit it really well on the back nine, where a 15-foot birdie putt I managed to hole across the green at the 10th was one of the key moments.”
MacIntyre, who was bidding to become the first player since Charlie Green in 1982-83 to win this event back-to-back, lost 4&3 to Elderslie’s Alasdair McDougall.
A week ago McDougall was in hospital having an abscess removed and is still feeling discomfort, but the 21-year-old was a deserved winner over his friend and travelling partner.
“We had actually planned to come up here together but that was before I ended up in the Paisley Royal Alexandra Hospital last Thursday night,” said McDougall, who is coached by former European Tour winner Dean Robertson.
After a scrappy start, McDougall took control by winning three holes in a row from the seventh, including the eight and ninth with birdies, as he earned a semi-final clash with Windyhill’s George Duncan.
Making just his second appearance in the event, 21-year-old Duncan looked to be heading out as he stood three down to Malcolm Pennycott from Royal Burgess on the 13th tee.
But, helped by a birdie-2 from 15 feet at the 17th, the former Dumbartonshire Stroke-Play champion turned the match around to win on the last.
“I’m still speechless that I managed to come out on top there,” admitted Duncan, who is on a golf scholarship at Lincoln Memorial University in Tennessee.
Andrew Burgess (Nairn) bt Jeff Wright (Forres) 2&1
Connor Syme (Drumoig) bt Craig Howie (Peebles) two holes
Alasdair McDougall (Elderslie) bt Robert MacIntyre (Glencruitten) 4&3
George Duncan (Windyhill) bt Malcolm Pennycott (Royal Burgess) one hole